The

am aware, it is the only perfect medium-sized vertebra
that has yet been found in Northumberland.
specimen, when it reached me, was imbedded in a thin
piece of shale, and both sides of the vertebra were
tolerably well exposed; but, in order to develop more
fully the more exposed side, and to determine absolutely
whether its vertebra was reptilian or icthyic, I rubbed
down the specimen, and found that the face of the
centrum was concave and solid, and that if a notochord
existed at all it is too small and indistinct to be seen
without a transparent section. The vertebra on the
opposite aspect to that described as having been rubbed
down is slightly convex and above the convex
centrum at the base of the neural spine there are two
moderately large, stout, convex processes, that do not
resemble those on the opposite side of the vertebra.
The total length of the vertebra is 9-16ths of an inch,
and the drawing represents in outline the rubbed down
side of the specimen, natural size. The solid centrum

is indicated by the letters; ab
the transverse processes; c the
zygapophyses, d the neural
canal; and e the spinous pro-
cess or neural spine. The
zygapophyses care each broken,
and the fractured extremities,
the impressions of which are
visible on the shale, are re-
presented by the dotted ends
of the processes.

The length of the vertebra in the antero-posterior direction is one-fourth of an inch; the sides are very slightly concave, and are marked with rather deep grooves, slight striations and minute pittings. I think it is probable that the specimen is either one of the posterior cervical or anterior dorsal vertebræ, as it is too short to belong to the caudal extremity.

This vertebra is much too small for any portion of the vertebral columns of Pteroplax, Orthosaurus, Macrosaurus, Amphisaurus, Anthracosaurus, or Loxomma, and too large for Ophiderpeton, Batrachiderpeton or Hylonomus, the only reptiles yet described as belonging to the north of England coal formation. I therefore venture provisionally to name the reptile to which this beautiful vertebral segment belongs Mesosaurus Taylorii-the generic name indicating the medium size of the reptile, the specific name being given in honour of the owner and finder, to whose industry with that of his co-worker and friend, Mr. John Sim, I am indebted for many of the best specimens I have had the privilege of examining.

T. P. BARKAS, F.G.S.

TRANSVERSE SECTION OF TOOTH OF
UNKNOWN REPTILE.

[1558] SINCE Professor Owen described the characteristic markings in the transverse section of a tooth of Labyrinthodon, the tooth of that new red sandstone reptile has become a stock illustration in nearly every work on paleontology. This does not arise from the fact that many other reptile teeth are not labyrinthine and elegant in their structures, but that comparatively speaking, little attention has been devoted to the microscopical examination of the teeth of paleozoic or mesozoic reptiles.

In addition to the reptiles referred to in letter 1456, jaws probably of other large reptiles have been found, among which are jaws with strong, ovoid, and slightly lanceolate teeth.

MAG.16 DIAM

NAT. SIZE

TOOTH OF UNKNOWN REPTILE.

Mr. Joseph Taylor, of West Cramlington, for the sec-
tion which furnishes these illustrations.
T. P. BARKAS, F.G.S.,
Newcastle-on-Tyne.

CERTAIN MATTERS MICROSCOPIC.
[1559] SECTION CUTTING INSTRUMENT (let. 1496,
p. 564).-I use Mr. Topping's form, and find it answer
the purpose very well. But the particular form of in-
strument matters little, since all that is required is
that the piece to be cut into slices shall be held firmly
against lateral pressure, whilst it can be raised through
a definite and measurable fraction of an inch. Mr.
White will be able to give "Achromatic" full infor-
mation as to his new resin.

Micro-Polariscope let. 1505, p. 566).-The great use
of the micro-polariscope is this-that it affords an
easy means of demonstrating the different "refrac-
tions" of bodies under observation. So far good.
The tyro has to learn by experiment often, sometimes
by book learning, the precise optical reactions given
by different bodies. Take cells supposed to contain
sphæraphide. It is often impossible to discover by
other than chemical or polariscopic tests whether the
cell contains those formations or a residual deposit of
essential oils. A chemical test could not be applied if
the object was mounted in balsam, or in medium, and
used to an unmounted object, would result in its
destruction. The observer applies his polariscope with
the prisms crossed; if the doubtful body shine out
more or less brightly on the dark field, he knows it is
not the oil residuum. He will now apply a neutral
test mica, and will ascertain the precise tint that the
body assumes. Supposing he be new to the work, he
will compare with its reactions those of the starch
cells of the tissue as seen in their normal state, and
those of the commonest forms of raphides and sphæ-
raphides.

FIG. 2

MAC. 4 DIAM

FIG.4

FIG. 3

find that certain vegetable cells in his section give "a negative reaction," and that these same cells olesys, wherever found, give that same reaction, whilst others are equally invariable in giving a positive restion. Take for instance the spiral fibre in the cell of rhubarb. That gives a negative colour-the starch comprises & positive one. Which is which? How shall learn which are negative and which positive? That is a problem which the authors of the Micrographie Die tionary" solve thus:-Those cells which, lying obliquely in the direction of a right-wound screw (when a "red" selenite is used), are tinged blue or yellow, while tho oblique in the opposite direction are red or yellow, be long to the positive class. In the negative class the order is reversed.

It would not be possible, I think, to give a list of different polariscopic reactions in such form as should be of use to the student withont tinted plates. The most that I dare attempt I have attempted, with, I fear, poor success, and that is to draw attention to certain quarters in which the polariscope is of us. The dent who desires to make himself master of the subjec will find in various works on optics-in various mont graphs by English, and especially German and Fre savants-the help which the limits of this periodical, and my own exceedingly limited knowledge of many branches of physical and natural science prevent my giving in this place. The scale of roach manifests substantially the same phenomena as that of the The former scale is commonly thinner than the latter and consequently has a greater refractive power. I have within the last few minutes carefully comparal a scale of each, mounted in the same way, and take quite at random, and so far as regards intensity of colour can discern but little difference between them I do not, of course, include the very thick portion of the sole scale immediately below the "teeth." I do happen to have a gudgeon scale. It must not be posed that I assert that there is no difference betwee the polarization phenomena of different scales. The of the same fish differ, as might be expected, their different sizes and thicknesses. Here polarised light would be of use in resolving the boundaries of th variations. Cui bono? That depends upon the We server.

To the microscopist it is of little service (apart from the correction of his lenses) to know that dense bodies The transverse section I have the pleasure of intro-refract an ordinary ray of light more than a less dense ducing to your readers is from one of the teeth referred body would do. But it does concern him to know that to, and does not belong to Pteroplax, Amphisaurus, these different refractive powers evoke easily observable or Orthosaurus, and the teeth of Macrosaurus are un- phenomena when polarised light is made use of. known. The section does not resemble in external will suppose that he has under observation a section form, nor so far as descriptions have been given in of vegetable tissue. A certain cell appears to have a internal structure, the teeth of Anthracosaurus or perfectly homogeneous wall of considerable thickness. Lozomma; it is probable therefore that it has been The polariscope shows only a very thin line. With taken from the tooth of an undescribed reptile. mica, a thin vividly coloured line is seen, and with it, on either side, a thin line of perhaps the complementary colour. He has learned that the one colour is that of cellulose. He concludes that he has a thin cellulose wall, and superimposes thereon a layer of a substance more or less dense, for the precise knowledge of which chemical test may be necessary. Or he may have a preparation of spinal marrow of sheep, as I have. By ordinary light it requires a high power, and very careful illustration to work out its details; by polarized light the whole is made plain as the prisms are rotated and the different refractions brought into play.

Fig. 1. represents a transverse section of the tooth
magnified four diameters; Fig. 2, a portion of the
same, magnified sixteen diameters; Fig. 8, the tooth
natural size; and Fig. 4 a transverse section, gin.
from the apex. The pulp-cavity in the centre
of the tooth is moderately large, and there proceed
from it radii of a willow-leaf form, which radii reach
the circumference of the dentine which forms the
substance of the tooth. A very thin coating of enamel
invests the entire tooth, but does not at any part dip
into the dentine, as is usual in the labyrinthodont teeth
of many sauroid fishes, and of some paleozoic and
mesozoic reptiles. Between each leaf-like process It may perhaps serve to make the use of the micro-
there are large pencils of dentinal tubuli, which extend polariscope more easily attainable if I give a few
to the surface of the dentine and fill the spaces be- general directions as to the mode of procedure. The
tween the leaf like radii before referred to. These tyro should first practise himself in the use of the
leaf pencils of tubuli are crossed by dark wavy bands, prisms alone. He should be able to procure a full and
which make the spaces resemble the ornaments on the brilliantly illuminated field when the optical planes
feather of a peacock, but still more resemble the fronds of the prism coincide, and a totally dark one when
of the marine algae Paludina pavonia. The lenticular they are at right angles; due care to the adjustment
radii have through their centres somewhat broad of the mirror will render this easily attainable. He
vermiform lines of semi-transparent and apparently should now examine easily-procurable starches,
structureless matter, which proceed from the apex to crystals and sections of the pith of such plants as elder,
near the base, and resemble to some extent the dock, rhubarb. He should note how far the lower prism
worm-like folds of similar lines which traverse the has to be rotated to produce a certain effect in a given
triple radii of the teeth of Amphisaurus amblyodus (see crystal, and compare that angle of rotation with that in
let. 1456). Opposite each indentation in the undulating an apparently similar crystal. He should especially
lines,pencils of tubuli emerge and enter, each infolding. note negative results.
Fine tubuliferous lines proceed from the dark spaces
on each side of the willow-leaf radii, and enter the
radii in the manner represented by the sketch.
Delicate curved transversed lines cross the radii near
their bases, and the tooth presents a singularly
ornate and beautiful appearance. I am indebted to

He should now make himself familiar with his series ef mica or selenite Alms without an object in the field. He must learn the proper setting of the prisms to produce the best colour. Then he must learn by heart the exact shade which each film gives, so as to detect any change produced by the objects under view. He wil

Mr. F. Blankley has called my attention to a of selenite and mica stages introduced by himself, but I must postpone any further reference to them next week. This letter is already too long.

I

H.P.E

FLUID LENSES-TO "THE HARMONIOUS
BLACKSMITH."

[1560] As our courteous and learned "Harm
Blacksmith" has thrown down the gauntlet, y
the challenge, and though very averse to p
name forward in print, I will, to the best of my y
tell him and our brother readers, briefly, my experie
with fluid lenses. In 1847 I took the trouble to t
Dr. Blair's experiments with chloride of anti
dissolved in muriatic acid, and put between two pla
convex lenses of crown glass, or between a plano anda
meniscus convex, exactly in accordance with the lev
directions, given in Vol. XIX., of " Edin. Phil. Tr
The lenses, which were of 2in. aperture, and ve
figured, gave 24in. focus, when the fluid was app
found that Dr. Blair was perfectly right as to the
total absence of secondary colour by such an ama
ment, but the large residue of spherical aberr
far more than overbalanced the advantage gained
absolute achromaticity, and no proportion of curre
foci of the lenses, which I afterwards tried, seema
mend the matter. It appeared to be a rule th
wherever a fluid, having less refractive power f
glass, was enclosed and in contact with spher
surfaces, forming an object glass, nothing
cations of this plan, and bad every informat
reduce the violent aberration. I tried many mod
that could be obtained kindly supplied by the
Mr. Robert Stephenson, M.P.; but I m
fess that no great results flowed from my efforts, and
I could not indorse the assertions of Profes
Robinson and Playfair, who, with one of Dr. Rar

He may also gain much information from Chambers'
excellent work on "Descriptive Astronomy" and from
Lardner's "Museum."

telescopes of 3in. aperture, and 9in. focus (it was
thus stated in one of the leading cyclopædias of
that day) "saw double stars with a degree of dis-
tinctness which surprised them." I take this from It appears that a radiant point, in addition to those
memory only, and regret I cannot give the name of already determined, has recently been found to exist
the cyclopædia; but 8in. aperture and 9in. focus must in Taurus. Professor A. S. Herschel, in a letter to me,
have been wonderful indeed, and I can only imagine says that "Schiaparelli in his report on the radiant
that the Dr. in doing this had arrived at the art of points of shooting stars, deduced from Zezioli's ob-
giving with certainty truly parabolic, or rather hyper-servations of 9,000 meteors at Bergarno in the years
bolic, figures. If I remember rightly, the power used 1867-1869, finds a distinct radiant po nt in Taurus at
was stated to be from 70 to 130 on this glass, and it R.A. 70°, N. dec. 20°, on the 10th of November. This
was a pancratic day eyepiece.
is not far from the place at R.A. 544°, N. dec. 16°,
noted by Mr. T. W. Backhouse, at Sunderland, as
the point from which a considerable number of
shooting stars radiated with great precision on the 4th
and 6th November, 1869, and which appeared very
probably to be the radiant point of the meteoric
shower to which the large meteor of November 6, 1869,
belonged."
WILLIAM T. DENNING.

Professor Barlow's experiments were materially different from the principle of Dr. Blair's, and had a totally different object in view. The great difficulty found at the time of obtaining good discs of flintglass, induced the Professor to try the corrective powers of bisulphide of carbon, which, as is well known, possesses a very high refractive and dispersive index; this was done by enclosing the fluid between two curved glasses, each having their convex and concave radii struck from the same, or nearly the same arc, and consequently resembling watchglasses; when confined by means of a glass ring at the edge the fluid was in every respect a highly dispersive concave, and to save diameter it was placed nearly half-way between the single convex plate lens and the eyepiece, the curves being so computed that it should intercept the primary cone at about half the diameter of the front glass, and also by its superior dispersive power make the correction for primary colour. A great improvement was also claimed by the Pro=fessor for the advantage of this plan in partially corerecting the secondary spectrum; this, however, did not turn out to be the case, and the late Admiral =Smyth (then Captain) had the kindness in 1850 to send me a small pamphlet containing the results of the ex-amination of the performance of the 6.8in. glass constructed on this system, by Barlow, for the Royal Society, at a very considerable expense.

"

REVOLUTION OF THE EARTH.-C. von Rikart

says: "On page 546, there is a note relating to my idea of a gas exuding from the earth, with reference to a balloon falling into the sea." The writer, quoting M. Paris, who says such a gas cannot have escaped chemists, says :-'If this gas is heavier than the air it will not rise. Then it could not influence the balloon, which did rise while over the land. He asks, is it lighter. Then it will diminish the density of the air, and the balloon will descend when over the land, and ascend when approaching the sea, as the gas would not exist in the air above the ocean. The italics under "He asks is it lighter" are mine; the others are his. He goes on to say: 'I believe that the air over the sea being rendered less dense by moisture, the balloon descends.' But is this the case when our air is charged with moisture; is it lighter or heavier, according to the amount of moisture in it?' 'In what manner would this affect the revolution of the earth?' he

Hon. Sec., Observing Astronomical Society. asks. I simply say a gas of any kind, no matter how much charged with moisture escaping from our earth, P.S. The remark referred to by "Hyperion' (let. 1885) that the fifth star in the trapezium in the as a gas escapes (if it does) from the earth, hotter or will give it a spinning or revolving motion. As soon nebula of Orion has been sought for in vain with 8in. colder, rarer or denser, it is mixed with our atmotelescopes and upwards, certainly does require qualifi-sphere, as water, hot or cold, let into the bottom of a cation. The statement was not meant to imply that bath mixes in the waters in that bath." the object was invisible to all instruments of greater aperture than 34in. It is, however, quite true that the star has resisted the power of telescopes of upwards of 3 in. aperture. It is true, also, that it has been seen without doubt, with the help of instruments very little greater in power than a 8hin. O.G. Certainly I failed to detect it with a 4in. O.G.

AN INTIMATION.]

[1562] In compliance with "Ferricum's" request (page 549, qy. 6646), I enclose a brief account of the usual method of analyzing iron and steel ores, but I must premise that it is not the method I use myself, but the generally used system. Full details can be obtained from "Fresinius" or other standard work on the subject.

ASCENT OF ROCKET.-TO"J. B. PRIMUS.”—“ J. B. Primus" (let. 1500) informs us that "a rocket will not rise, nor a Catherine-wheel turn in vacuo." What does he mean? Is the resistance of the air the sole cause of the ascent of the rocket? Would not a rocket ascend in vacuo by reason of reaction to the downrush of heated gas from its orifice? If a gun were fired in vacuo would there be no recoil? Is the recoil due to the resistance of the air to the flight of the ball, or is the recoil the appropriate reaction to the forward motion of the bullet? Can there be action without reaction ?-A. J. V. G.

64

LUNULA OF HIPPOCRATES (LET. 1426, pp. 520, 570).-M. PARIS is wrong in supposing that Hipparchus discovered the quadrature of the Lunula; as "AntiquaYour other correspondents must excuse my not at-rian" says, it was Hippocrates, of Chios, a celebrated tending to their respective queries just at present; and geometrician, who lived about 500 years B.e. Hippo to your querist "P. J." (page 551, qy. 6729), I would crates, of Cos, a celebrated physician was born about observe that his query must be a little more detailed 460 years B.C. M. Paris seems to have assumed that before I can answer it in a satisfactory manner, as I Antiquarian" referred to the latter, although he was must have some idea of what he wishes to analyze the not a geometrician. It may be mentioned here that phosphate of lime for, and also if he has any practical Enopides, of Chios, is stated to have been the disacquaintance with quantitative analysis. coverer of the lunula. However this may be, Hippocrates has generally had the honour of the discovery attributed to him, and the figure still bears his name, being commonly denominated the lune of Hippocrates. -A. J. V. G.

URBAN.

2nd. The performance of the telescope was very variable, from change of temperature, and also, as I take it, from currents in the fluid caused by sudden alteration of position, no doubt consequent on local change of temperature. Polaris, when tried side by side with the celebrated Hartwellian 5.9in., and by Captain Smyth himself, gave in Barlow's 7-8in. a beam of light towards the north; and Rigel, with a power of 450, was nowhere, the rings of the spurious discs being broken by disagreeable rays. Part of Barlow's failure EXTRACTS FROM CORRESPONDENCE. might no doubt have arisen, as the late Admiral justly remarked, from errors of workmanship in the figuring of the surfaces to which any telescope might be more or less liable; but evidently the greatest part arose from the application of a highly volatile fluid subjected to every fluctuation and change of atmospheric disturbance, and, if I may be allowed the expression, like mercury in a barometer, to inequality of pressure and heat.

In 1866, I took out a patent for correcting the secondary spectrum, principally by the use of a fluid cement placed between two lenses of flint and crownglass, and having a meniscus convex action. The fluids used were principally oil of cassia let down to the right dispersion by castor oil; and when properly done, and the curves nicely balanced, nothing can surpass the performance of such glasses, the whole of the colour being entirely destroyed under any power, and the spherical aberration completely corrected; but alas! the same varying atmospheric conditions have disappointed me, as they did Dr. Blair and Professor Barlow; and the process of re-cementing the lenses would have to be done every few months, which is a detestable thing in a telescope, where permanency should be of the highest importance.

With respect to the cementing of coincident surfaces of an object-glass for the purpose of saving a little light, I have found no objection in small sizes'; but the advantage gained is not of very material moment, considering the perfectly pellucid glass, and the refined mode of working the surfaces which is now employed. B In conclusion, I may tell our "Harmonious Blacksmith" that so far as I have seen of fluid lenses, I am afraid that little can be done (from the causes above pointed out) to advance either the power, convenience, Gr cheapness of the refracting telescope; and, I think, to those about trying fluids as correctors of chromatism, I should, from my experience, give the advice that Punch once gave to those about to marry-" Don't." I shall be happy, at any time, to answer as well as I can any question asked by brother readers on similar > matters. WM. WRAY.

TELESCOPIC WORK, ETC.-As we desire this con-
troversy to cease, we shall only give the following ex-
tract from "Mr. F. Denning's" letter:-" Of course
when I said that I could contribute to your pages an
original article on almost any astronomical subject, I
meant that I could lay before your readers (without
copying from the writings of "F.R.A.S." or anybody
else), a portion, at least, of the knowledge which as-
tronomers possessed of the science. Can "F.R.A.S."
do more? I should imagine that he could not, and
that even when he has done this he cannot help feeling
others have availed themselves of the knowledge he has
proved himself to possess, and he is, as a consequence,
sometimes unduly harsh in his criticisms of their
literary efforts. But I do most sincerely dislike all
argument that has not for its object the advancement
of science, and so shall have nothing further to say in
the matter."

ARTIFICIAL JEWELLERY (p. 529).-M. Paris
says: "In 'Jardine's Naturalists' Library,' the common
bleak is stated to be the fish the scales of which are
used in the manufacture of artificial pearls. I do not
bleak be called a flat fish?"
know whether blay' is a synonym; if so, can the

WILLOW LEAVES.-M. Paris says:-"I have a
small field glass, and with a lens belonging to a micre-
scope used instead of its eyepiece, the surface of the
moon appears covered with bright willow leaves about
one twentieth of her diameter in length; the usual
markings and craters being fused together, as the
telescope is out of focus."

THE CONING OF RAILWAY WHEELS (Let. 1451, p. 540).-M. Paris says: "R. H.' does not seem quite up to his subject. The wheels of railway carriages are not free to move on their axles, and the coning is intended to counteract the centrifugal force and to prevent sledging."

THE ENGLISH MECHANIC ABROAD.-"Saul Rymea " says:-"It may gratify our friend Jack of All Trades,' to know that his method of straightening saws RADIANT POINTS OF METEORS. is being extensively circulated in America. I saw it in [1561] PARTICULARS of the meteor which was ob- the Iron World, which credits it to the Cabinet Maker. served by your correspondents E. W. Spiller (1452) Mr. Gormley's method of polishing shirts and collars and "Aerolite" (1458) on February 18 last, will be has been honoured (?) with insertion by the Scientific contained in the next report of observations made by American; but, as usual, without acknowledgement. the members of the Observing Astronomical Society. These are only two of numerous instances which I have There appears to be some differences in the descrip- noticed lately. I suppose your Transatlantic contemtions of the meteor, as given by the two correspondents poraries are welcome to the information contained in I have named, for while Mr. Spiller says that "no 'our' journal, but I think they might specify the bright track was apparent," "Aerolite" distinctly source whence it is derived. I imagine they would states that the meteor left a train which was" visible find a difficulty in filling their columns without using faintly some time after." At Bristol, the train left by the matter of their British contemporaries. the meteor at its disappearance was distinctly seen as a nebulous patch for fully ten minutes. "Aerolite" will find a list of the probable dates when meteoric showers may be expected in Humboldt's work on astronomy (dated 1866) translated by Sabine.

The

Scientific American, a journal notorious for stealing the
information of our English papers-particularly the
ENGLISH MECHANIC-received recently a rather severe
dressing from Engineering, for an article on its British
contemporaries, which was simply impertinent."

REPLIES TO QUERIES.

In their answers, Correspondents are respectfully requested to mention in each instance the title and number of the query asked.

[5938.]-VARNISH FOR FISHING LINES(U.Q.)-The following is an old recipe:-Half pint boiled oil, quarter pint mastic varnish (turpentine, not spirit), quarter rosin of bulk of oil, quarter pint copal varnish; melt all well together; soak the line for two or three hours, and hang out to dry for a month or two; but a few years ago I tried plain copal varnish, and found it answer well

for a silk line.-AN OLD SALMON FISHER.

[6074.]-THE AIR GUN (U. Q.).-I am sorry this query so long escaped my notice. If" W. G. S. S.," &c., refer to Vol. XI., page 596, they will find another illustration intended for answer to "A Hunter's" query. The engraver has diminished the size of the original drawings, which were for a cane lin. diameter, and has also engraved a superfluous blot near E. Further in

formation will be readily given.-T. A.

[6118.)-STEAM ENGINE (U. Q.).-You cannot utilize so small an engine; it is too small in the bore. Had it been three and five you might have done what you wanted with it.-JACK OF ALL TRADES.

[6141.]-TREATING WOOD (U.Q.).--You can ebonize wood by treating first with hot lime-wash newly made; when dry well brush and lightly glass cloth with fine cloth. Treat after with logwood and nut galls in powder-lb. the former to lb. of latter. Pour half a gallon of boiling water upon each separately in an earthernware pan or basin. Do not put it in anything metallic or you will spoil it. Pour off half, or a quart, from each, and boil the chips and galls with another 8 pints for an hour or two; when cold put pint methylated spirit into it. It will keep for years. Dress your timber with it two or three times. Rub with fine glass cloth to take the burr off; wet again. Lastly, with vinegar, in which you have digested old rusty nails; it will be as black as jet. When dry, oil and polish. After dressing lime for white, use white lead finely washed, whiting equal parts, put on with very clean turps and copal varnish that the colour may dry dead. Glass cloth and polish after two or three coats.-JACK OF ALL TRADES.

[6143.[-CEMENTING SPONGE TO BRASS (U. Q.). Some years ago I had a job to do fastening some cloth to iron, brass, and copper. The compo. was loz. sulphur and 4oz. or 5oz. of linseed oil. It makes a tough elastic cement, very much resembling india rubber, only deep red. I have had no complaint, and therefore have reason to believe it answered every purpose. Spirits will not fetch it off. Try it for sponge.-JACK OF ALL TRADES.

[6149.]-DRIVING-PULLEY BELT (U. Q.).—1st, you must undoubtedly throw a greater strain upon engine; second, there is a composition used for translating, and can be had at most leather-sellers and repairers of gutta-percha boots. It answers well for patches, I can

tions of rockets used in the service, the chief of which
[6543.]-WAR ROCKET.-There are several descrip-
mostly used; it has no stick, which the others have, but
are Congreve's, Boxer's, and Hale's. The last is now
is steadied in its flight by a small metal fan-like arrange-
ment, at the rear upon which the fire acts as it rushes
from three holes, thus producing a sort of "screw
motion in the rocket, exactly like that of a conical pro-
jectile fired from a rifle. Rockets are of different sizes,
such as 3, 6, 12, and 24 pounders. The case of Hale's
rocket is of corrugated sheet-iron, filled with the
following composition (for 24 pounder rocket). Salt.
petre, pulverised, 275 parts; sulphur, sublimed, 49
parts; charcoal (alder) ground, 75 part s. The fore part
Hale's 24-pounder rockets have a range of about 5,800
of the rocket contains a bursting charge of gunpowder.
yards, when fired at an elevation of 87°.-ARTILLERY
CAPTAIN.

[6546.]-AIR PUMPS.-Discharge pipe to prevent any
dirt or dust from interfering with the valves.-JACK OF
ALL TRADES.

[6549.]-VERGE ESCAPEMENT. I should think by this query that you know very little of watch work, as you state your query in a very non-practical way. I suppose you require to know how the verge pivot holes are drilled perfectly upright. The way to do so is, having depthed one end of the verge correctly (say) the top or cock hole, take the upper plate and screw the cock very tight, put it in the mandrel with the centre in the hole you have just drilled; take out the little slip of brass with the endstone in it, and with a graver centre very carefully the potance; drill a small hole (hold the drill and turn the mandrel); this is for the foot hole of the verge. If the watch you have has got holes which are worn large, first brooch out one of the holes to a good size, and put a piece of brass wire in so as to stop the hole up and hammer it well, then in the mandrel as above, centre, and drill this bush reverse sides, and do the other hole just the same. I will answer you more fully if you will say what you require to know. TOMETER.

[6551.1-HALF DEAD-BEAT ESCAPEMENT.-In enclosed rough sketch of a half dead-beat clock escapeanswer to "A Young Clockmaker," I beg to send the ment, which I trust he will find sufficiently clear to pallets, b is their centre, and that should be kept as low understand. Cis the escape wheel, and athe half dead as possible, as by doing so you get more motion in the pendulum, than if the centre were high. Having dePermined what number of teeth you wish to escape your pallets over (seven is a very good number) from the centre b describe the short arcs 1 and 2, so that they will just take in seven teeth of the escape wheel; then from the same centre describe the arcs 3 and 4, so as to leave the pallets just the width to go freely between the teeth of the wheel; next file the slope on each pallet, the one from the inside

of either leather or cloth that has not been previously and, the other from the outside, harden and polish the that one or two is what is wanted; and it is desir

[6605.]-PLANTING POTATOES.-As one, or pr two sets of each potato at some time in its growth t the lead, and all other conditions being equal ke pallets and they will be ready to plant. It is merely during its growth. Hence it follows that to ent that it has as little check as possible at any and al the part that acts in the wheel that requires to be deprives it of that sapport necessary until the hardened, and the best way to do it is with a blow-pipe supply it from the earth. In fact, the supply and a piece of charcoal, and I prefer oil instead of water within the potato goes to make these roots, and a to harden small things in.-HENRY CHAPMAN.

[6558.]—ROMAN CEMENT. Of course "Doggers" knows what cement stone is. Let him take equal parts of coal, slack or breeze, coke, two to one of the stone, broken small; put into a circular kiln or stove lined with brick, or ordinary lime-kiln; when burnt out, separate from ashes and grind with edge stones or mill stones. The clinker, if burnt enough, looks very much like burnt cork.-JACK OF ALL TRADES.

[6556.]—RAISING WATER.-This question is imperfectly stated, but if, as I conjecture, it is intended that

duced more in a given space if parted than if left to grow together. The late A. Knight, Esq., carrying out this plan grow the largest crop recorded-thirty-three tens per acre-in, oak-lenves. My former answers, it should be observed, were taken from the best authorities, giving no opinion of my own, and were also confined to the time of the year (January), otherwise I should have stated that the sets are better in earth until the moment of planting. That autumn planting is better than spring planting, and that the sets are better for being cut at lifting, whether planted at once or placed in earth until spring. But the way "G. M.'s" question is put involves my giving a reason, and who am I to sit in judgment? My native town is celebrated for its, gardens - aud amateur gardens-there being nine or ten thousand of the former around and near, and where meetings are held every evening in the year at some one or more places to arrange for exhibitions, &c., and so it becomes a sine qua non that the best potato, that the best part of such, together with every available means, should be used to gain success. Tales are told of one who did not hesitate to uncover his household bed to cover his horticultural bed from too much rain, at the time it (moisture) was not wanted. This day, and for some weeks on Mondays, numbers may be met taking the sprouted potatoes, cut, uncat, in sand, sawdust, rooted green, just as the fancy has taken. Some have started them beneath the fire-grate, or by the side of the firedone everything to win.-ROLAND.

[6612.)-CLEANING BRONZE FIGURES.-If metal, brush with hard brush and a little linseed oil; put them out of the dust for a day or two afterwards; if plaster, bronzed the same with a soft brush.-JACK OF ALL TRADES.

burning in your tent you can keep them out. I can
keep mosquitoes out of my bedroom by filling it, the
windows wide open, with the smoke of coarse brown
paper, and after dusting curtains, bed-valance, and in
five minutes closing windows and not again opening
them when a light is in the room. The best anodyne I
have found for mosquito bites is Goulard water: equal
parts of olive oil and Stockholm tar well shaken together
and smeared over back of hands, eyebrows, and about
nose and behind ears, will keep these pests off; perspira-
tion will carry it off, necessitating a renewal. Soap and
water washes it off.-R.

[6641.]-DRILLING MACHINE.-"Hempstead" will
have difficulty in getting an efficient hand machine for

#

80 per minute; length of boiler for ditto, 7ft.; diameter,
2ft.; connecting rod, three times length of stroke;
cutting off steam, stroke.-JACK OF ALL TRADES.
[6649.]-DYEING KID BOOTS.-In the treatment
of leather, especially white, it is difficult to get the dye to
take properly. Damp first with lime water and sponge,
rubbing them lightly. Do not saturate them or you will
not get them into shape again. Stand by in the shade
to dry; get some elder bark and make a strong tea, and
dress them two or three times; after strong decoction of
logwood and nutgalls. Finish with good ordinary black
ink; sponge until bright with a little card soap. It is a
delicate job at the best of times.-JACK OF ALL TRADES.

[6649.]-DYEING KID BOOTS.-I should like "H. P. K."to try the following for dyeing his kid boots : -Take toz. of quercitron bark; oz. carbonate of potash; oz. cudbear; and foz. beeswax (scraped). Mix the above with about pint of boiling water, then add 3 pints of strong boiling logwood (put 2lb. of logwood in 8 quarts of water and boil the same till it is reduced to 8 pints); strain the whole through a very fine sieve and bottle it for use. Apply when cold with a sponge, rubbing very even,and when dry rub them with a clean cloth and he will have a splendid black, and likewise a splendid gloss, the cost of which will be as follows:Quercitron bark, 1d.; carbonate of potash, 1d. ; cudbear, 1d.; beeswax, id.; logwood (21b.), 6d.; total, 104.HENRY MARTELL.

[6652.]-DRILLING WROUGHT IRON-I use water or oil indiscriminately; just which comes to hand first. -TOMETER.

[6652.]-DRILLING WROUGHT IRON.-A mixture of soft soap and water is commonly used, and is better than oil, as well as cheaper.-EDWIN HOLMES.

(6658.]LEKEYO ISLES.-Spelt Leköe-off the Coast of Norway, lat. 65° 5 N., long. 11° 40 E.-ANON.

[6614]-GLASS WATER-GAUGE.-It is the small diameter of water-gauge tubes which enables them to bear the strain, since this, with given pressure, increases in proportion to the surface acted on, so that an inch tube will require to be just twice as strong as a half-inch tube to bear the same steam-pressure per inch. Again, a tube will bear a much greater pressure than any flat or curved surface, because the strain is one of mere tension, which glass will resist to the extent of about 2,000lb. to the square inch; but in all other forms there is a cross strain which throws unequal stress on the different portions, and causes one part to enclose sketch of an efficient hand machine for general it is that without the presence of which nothing will act as a lever against other parts, by which, of course, a great deal of the actual strength of material is lost, and the substance of it is fractured at a far lower pressure than it would have sustained in a tubular form.J. B. PRIMUS.

[6622.]-BRONZING CHANDELIERS.-Red bronze 'is produced by dipping in aquafortis, into which some old iron nails or rust is put, which gives it an appear auce; afterwards it is dressed with Venetian-red and stale beer, and well brushed, wiping the mixture off the prominent parts.-JACK OF ALL TRADES.

[6628.]-BATTERIES FOR ELECTRIC BELLS.-The Leclanché would suit the querist better than the modifiled Daniell's he has used, and be less expensive. The period of working depends wholly on the quantity of material in the cells. It is decidedly less troublesome in every way than the Dasiell. It is simply a common manganese cell, and what the patent is seems very doubtful indeed. Particulars of construction with drawings, &c., were given very fully in Nos. 294 and 296. I may say that I hope soon to give description of a cell which will have many advantages over the present forms. "M. P. S.," qy. 6576, asks me for a description of the Leclanché which he says I have promised, though I certainly have not, seeing that I do not think it fair to careful and regular readers to continually repeat the same information, which, in this matter, has been not only given as just referred to, but also as fully as it lay in my power in my series of papers on the various cells. This is, in fact, the first of the series of mistakes likely to arise from a new correspondent signing "Signus," which will be mistaken by many readers, and still more often by the compositors, for my signature.-SIGMA.

[6626.]-CASTING LEADEN PLUMB-BOB.-I imbedded an egg-shell in some sand with which a flowerpot was filled; over the hole in the shell I placed a wire loop, one end of the loop being in the shell; I then filled the shell with molten lead, and I thus, with very little trouble, had a perfect bob ready to tie on to the Eline of my level.-E. B. F.

Solution:-We know that " being the the roots of the quadratic equation r+p+qo, we have +" =-pr"=q; hence, when we have the sum and the product, we can always find the equation of which the required quantities are the roots. Now, from (3) and (4) I have wy; (1) gives the sum, hence w and y, putting these values in (2), I obtain +, and (4) gives the product, hence x and .-BERNARDIN.

[6840.]-MOSQUITOES.-The best way to kill mosquitoes, after they get into the camp, is to shut up every crevice, and burn a pound of waste or sheepwash tobacco. To keep them out, burn dry cow-dung at the door of the camp. Proved.-M. P. S. [6640.]-MOSQUITOES.-II "J. L. T." will sponge his hands, face, and neck with vinegar, he will find it an excellent protection against mosquitoes, gnats, and even fleas and bugs.-Vox.

[6640.]-MOSQUITOES.-Let me tell "J. L. T." that it is almost impossible to keep mosquitoes out of a tent. I know from long experience that you can't keep them out of your bunk on shipboard, with a muslin curtain or mosquito "bar" as it is called, when lying in the fresh water rivers of the East Indies, much less out of an open tent on shore. But you can prevent them from biting by anointing the exposed parts with oil of mustard seed; it is quite harmless; I have used it over and over again in the East Indies. To cure the bite, press the part with the end of a key and apply a drop of brandy.-AN OLD SAILOR.

(66-40.]—MOSQUITOES.-I do not think if a light is

I

drilling 1in. holes, especially in wrought iron. The best
for general purposes I find is the ratchet brace, but
work, which will, I think, explain itself.-W. H.

[6641.]-DRILLING MACHINE.-Use a ratchet brace
and a drill turned down to shoulders like a pin drill. I
have used them first step after drill point, which has
been in., the next shoulder using 8-16th, making th,
and the next 1in., until I have drilled a 8in. hole with
a 6in. lathe, single gear, and bored a pair of lathe heads
out of steel bushing under the bridge of the fire-place
with a ratchet brace and such a tool.-JACK OF ALL

TRADES.

[6642.j-MAINSPRING.-A going barrel with the stopwork off ought to make five turns; as the spring is armed half a turn, and the stopwork allows it to make only four turns, there will be half a turn over to prevent its being wound up tight.-NOBODY.

[6642.]-MAINSPRING.-About 14 or 16 turns of mainspring should be coiled in the barrel. If you want a more lucid explanation please state what you mean more clearly.-TOMETER.

[6648.]-PROJECTILES.-I send particulars of a round fired at Shoeburyness, on the 21st November, 1868, which I believe was at that time, the greatest range of any gun, and I have noticed no other piece that has since carried so far. The gun was a steel Whitworth, weighing 14 tons 10cwt.; the calibre major axis, 9025in.; calibre minor axis, 8-250in.; length of bore, 140-06in.; length of gun over all, 163-80in.; rifle spiral, one turn in 171in. The projectile weighed 250lb., was fired with a charge of 50lb. of powder, and with an elevation of 83°, the range was 11,243 yards, or six miles and 683 yards.-L. H. O.

[6645.]-SIZING CLOCK PINIONS.-If the teeth of wheels are cut, and he requires size of pinion to match wheels, having determined the number of teeth of pinion, he can proceed as follows:-For a pinion of 8, gauge off 8 full teeth of wheel, which will be diameter of pinion; for ditto 7, gauge 3 full teeth and quarter of space between teeth; for ditto 8, gauge 4 teeth on the points; for ditto 9, gauge a little less than 4 full teeth; for ditto 10, gauge 4 full teeth; for ditto 12, gauge 5 full teeth; for ditto 14, gauge 6 on the points; for ditto 16, gauge 6 full teeth; or if he wishes to work by rule of thumb, add two to number required in pinion; divide that by three, which, ganged off wheel, will give diameter of pinion.-A COUNTRY CLOCKMAKER.

[6645.]-SIZING CLOCK PINIONS.-The pinions are gauged by means of a sector.-TOMETER.

[6645.]-SIZING CLOOK PINIONS.-In answer to "Middlesbro" I am sorry I cannot give him the mathematical rule for sizing pinions to wheels, and wheels to pinions, but I can tell him the method usually used by working clockmakers. There is an instrument called a sector (it looks something like a brass rule), and it is divided into the various numbers that are commonly used for the teeth of clock wheels and pinions. The way in which it is used is as follows:-First-Of course, you must calculate what number of teeth you will have in your pinions and wheels; I will suppose that the pinions are made first and that they have eight teeth, or leaves, as they are usually called; you open the sector until your pinion will just go in where the figure 8 is engraved. I will suppose the number of teeth in the required wheel to be 96; to find its diameter look down the scale on the sector, and wherever the required number is engraved will be diameter that the wheel must be.-HENRY CHAPMAN.

[6647.]-BEET-ROOT SUGAR.-To obtain crystallized sugar from beet is a very troublesome process, only practicable on a large scale, and, therefore, I presume, beyond the means of "Home Produce." If he wants only sweet liquor he may obtain it by boiling down the expressed juice to nearly the consistency of treacle, and filtering once or twice through bone charcoal. To tell him how to make sugar would take a column to little proft.-J. B. PRIMUS.

[6648.]-TWO-HORSE POWER HORIZONTAL ENGINE-Boiler pressure, 80lb. per square inch; diameter of cylinder, 4in.; length of stroke, 12in. No. of strokes,

[6653.]-LEKEYO ISLES.-Probably Liéon-Kićou, South of Japan. 2nd question: Dr. Thomas Burnett was born in 1635, at Crost, in Scotland, and died 1715 Master of Sutton Hospital, London.-BERNARDIN. [6655.]-OXYGEN BURNING IN HYDROGENOxygen is not an inflammable gas, and will not barn; but burn. Hydrogen, on the other hand, will burn, and in so doing unites with oxygen and assumes the form of water, as may be easily seen if a jet of hydrogen be burned at the bottom of a long glass tube, the sides of which will speedily be coated with a dew and will at last run with drops of water, formed by the anion of the two gases in process of combustion.-J. B. PRIMUS.

[6655.]-OXYGEN BURNING IN HYDROGEN.Oxygen may be burnt in an atmosphere of hydrogen by the following method:-A piece of glass tube, a foot or so in length, and about an inch in diameter (a paraffine lamp chimney will do), is fitted with a good cork at each end. Into one of the corks is inserted a short piece of glass tubing, tin. in diameter, to which is attached a piece of caoutchouc tubing provided with a pinch cock. The other cork is perforated, and a metal tube 2in. or Sin. long, and jin. diameter, is inserted, but The tube is filled with does not pass through it. hydrogen. For this purpose it is fixed upright, metal tube downward, and the gas is passed in at the top through the eaoutchouc tube; when full a light is ap plied to the gas at the extremity of the metal tube and the pinch cock turned until the supply of gas is reduced so that there is a small flame only from the metal tube. A glass tube about fin. diameter, and terminating in a moderately fine jet, is now connected with a bag or gasholder containing oxygen, the oxygen turned on, and the glass jet with the issuing oxygen passed through the metal tube into the glass one, when the oxygen, lighted as it enters, will burn in the glass tube containing hydrogen. Care must be taken that the larger tube is completely filled with hydrogen before the burning oxygen is introduced. In passing the jet through the metal tube it should not touch the latter, or may be extinguished. With slight modifications in the above apparatus air may be substituted for the oxygen and coal gas for the hydrogen.-HYDRIC OXIDE.

[6655.]-OXYGEN BURNING IN HYDROGEN.-I have seen a jet of oxygen burn in an atmosphere of hydrogen, or I should say coal gas, which was used for the experiment, which was performed as follows:-An

B

f

inverted jar A, open at both ends, was connected with the source of coal gas by a flexible tube B, which was attached to the upper end F; the jar was held in a vertical position by a Bunsen's holder C, so that when the gas was allowed to enter at the top it would 'How downwards and displace the air in the bottom of the jar. A large cork was fitted loosely, and through this there is passed a small glass jet connected with a gas gas. To perform the experiment, first remove the cork bag filled with oxygen, having a weight to press out the and oxygen jet and turn on the coal gas, after a few seconds light the gas at the bottom of the jar, it will burn at the mouth with a faint blue flame, then at onco insert the cork and jet (the oxygen being previously turned on), it will take fire and burn in the hydrogen, which will be extinguished by pressing the cork into the jar. It will also be noticed that the upper part of the jar has become covered internally with dew, owing to the combination of the two gases and the formation of water.-F. M. NEWTON.

tube with oxygen issuing from it; the oxygen will ignite requires to adapt the higher pressure in his boiler to on the surface of the wire cloth. The reason why it on passing through the hydrogen flame, and when in side the jar, the oxygen will be seen to burn in the atmosphere of hydrogen.-A. Z.

be given to this query, since friction, weight of
[6687.]-MOTIVE POWER-No positive answer
accuracy of permanent way, will all affect the rig
But making allowance for these, the draft of sta
the weight to which it rises in a given distans, d
on an inclined plane will equal its weight multiplied
divided by that distance.-J. B. PRIMUS,

[6689.]-RIBAND OF BRUGES.-It is e With four-made by dissolving a small portion of nitre in a ENGİN quantity of perfume, then take the riband and eaten it with the mixture; dry, and make up in small rok use it, light, and then blow it out, when it will smoulder away, while diffusing a pleasant perfuzeT. F. DALY.

the other is in contact with line wire, trans being depressed one pole of his battery being t current which, on arriving at B, enters the be key, which being in contact with the bridge, the passes to his bell and from thence to the th completing the circuit. The same effect is of produced if B's key be depressed. The currest, be observed, does not ring the sending statio being disconnected from the line until again pati cuit by the key being raised. This is an obvisen udta tage, as by such arrangement the resistance of coils at B have only to be considered. Dis STO plan of the key.—SIGNUS.

[6692.]-ELECTRIC BELLS.-I G. Harvey's are such as generally sold at the shops for electric bells they will be useless in manner w requires to work them. What is technically is switch key would be essential; this would enable the to be rung from either side with one battery. key. G. Harvey requires a return line wire r willingly give a description with diagram of the d line. The first would be essential if an earth tainable. This is easily procurable if a waterf battery I should think it would act adm main is on or near the premises. As regards & E