aboat results at once most creditable to the manufacturers and most economical to the pracsical cultivators. We have, in relation to this topic, an anecdote or two to remember. A Devonshire farmer invented a modification of the rotatory churn, in which, by making it revolve in an outer casing of warm water, tempered by the aid of the thermometer, he could at all seasons of the year command the best degree of warmth for separating the butter, and thereby complete the process in a time at once brief and uniform. A French "inventor" saw the model. Forthwith, he patented it for all Europe at Paris, sold the idea to a Scotchman, and enriched himself through an Ayrshire medium by help of the "Incomparable French Churn." A Yorkshire smith, living in the midst of heavy land, fixed harrow teeth into a long cylindrical axle at uniform distances, and fitting two of these axles together, so that the teeth of the one should play between those of the other when it was dragged over the field, tore all the brittle clods to pieces. The invention was never patented, and so came back to us at our great agricultural show as a marvellons Norwegian harrow. Again, the Americans have adopted many English and Scotch ideas, especially in the matter of reaping-machines, for the whole history of which we may consult the Journal of Agriculture and Transactions of the Highland Society of Scotland, for January, 1852.

THE SUN'S COLOURED PROMINENCES.
BY RICHARD A. PROCTOR, B.A., F.R.A.S.
Author of " Other Worlds than Ours," &c., &c.

IN TWO PARTS. PART II.

Wapproaching, Lieut.-Colonel Tennant urged

THEN the great eclipse of August, 1868, was

clouds, or as those liquid drops or vesicles* which prominences shows a spectrum of bright lin
form the cumulus and rain-clouds. If the rain- new and more hopeful method of research is t
bow-tinted streak appeared, but was crossed by diately suggested. For the spectrum of the
the solar dark lines, then it would be probable from the illuminated air is, of course, the
that the prominences shine by reflecting the solar in character as the solar spectrum. The
light. While lastly, if bright lines made their scope treats the two kinds of light very diff
appearance it would follow that the prominences It takes light from the illuminated au
consist of glowing vapour, and the nature of the spreads it out into a long rainbow-tinted st
vapour or vapours of which the protuberances The more we increase its power, the longer
are constituted would admit, perhaps, of being streak becomes; but it must needs grow fautet:
recognized if the exact position of the bright lines the process: for we cannot get more light in
could be determined.
spectrum by adding to the dispersive powe
our spectroscope, and, therefore, the mor
spread our light, the fainter the intrinsic lust
the spectrum must become. But when the spee
scope has to deal with the light from a co
prominence (or with any light showing tra
lines) it simply divides it into a definite a
of distinct portions. It takes the red part of r
light, and sets that in one place; it takes '
orange and sets that in another; and la
takes the blue (I consider only the brig
lines) and sets that in a third place. Hver
crease its power it still does the same, only
distance between the three divided portions is
increased. Thus they remain as bright as bac
but farther apart. Now, in the actual case d
spectroscopist who attempts to see the pro
nence-lines by full sunlight, the two specs yr
dealt with together. There is the rainbow-a
streak (crossed by fine lines, representi
illuminated atmosphere), and there are the tr
bright lines representing the prominence, P
obvious that if we increase the dispersive p
of our spectroscope, we must increase our chan
of seeing the bright lines; for we only throw fo
farther apart, whereas we actually reduce
luminosity of the rainbow-tinted streak.
Now Janssen felt that he could spread i
brilliant lines, which he had so admired cu
atmospheric light out sufficiently to render

It will be understood, therefore, that the ob-
servers awaited with the utmost anxiety the ap-
proach of the totality. The German astrono-
mers at Aden had the advantage over the English
and French astronomers in one respect; for the
shadow reached them some forty minutes or so
earlier, and they, therefore, first of all men, became
acquainted with the true answer to that question
which had so long awaited solution. Indeed, if
actual priority should in this case, as in some
others, determine the award of full credit for a
scientific discovery, the German astronomers might
claim to be alone associated with the recognition
of the true nature of the coloured prominences.
For by the time Tennant and Herschel had just
solved the problem the Gor nans must have fully
discussed and, as it were, digested the great dis-
covery. Of course, however, no such unjust
award has been made. The credit of the discovery
has been equally shared among all who indepen-
dently effected it. The Aden observers, Tennant
at Guntoor, Herschel at Jamkandi. Janssen and
Rayet at other Indian stations, alike succeeded
in learning that the spectrum of the prominences
consists of bright lines, or, in other words, that
the prominences are formed of glowing gas. All
the observers agreed in announcing that three
glines-one one prone, ne spectrum.
bright lines-one red, one orange, and one blue
But while some could see no other lines, others
saw five or six lines, and M. Rayet saw eight or

The nine.

From a comparison of the various observations it was concluded that the red and blue lines were the well-known C and Flines of Fraunhofer, both belonging to hydrogen, while the orange line was referred to sodium, or, in other words, was held to be coincident with the double D line of Fraunhofer.

While the eclipse was actually in progress, a brilliant thought occurred to one of the observers, and on the following day that observer was searching round the sun's disc for signs of prominences in full sunlight.

M. Janssen had been struck, like all the observers, by the brilliancy of the lines which formed the prominence-spectrum. "Immediately after the totality," he says, " two magnificent protuberances appeared. One of them more than three minutes (80,000 miles) in height, shone with a splendour not readily conceived." As he looked, he felt convinced that these lines might be seen when the sun was not eclipsed; and he cried out, he tells us, "I mean to see those lines again." The principle on which his hopes depended is not difficult to understand.

the eclipse, distinctly visible. On the very after the eclipse he had completed his arran ments for the purpose. He turned his instr ment towards the sun, and he obtained the resu he had anticipated. The bright lines in the pro minence-spectrum were seen with perfect es and he was able, by comparing their posit with the position of the solar dark lines in spectrum of the illuminated atmosphere, to de mine their real position in the spectrum. H found that the two lines he had supposed to identical with the double D line had a suga different position-in other words, the car sponding vapour was not that of the sodium. But the lines he had associated wit the F and C lines of hydrogen were act identical, he found, with the dark lines which dicate the presence of hydrogen in the atmosphere. Hence it was proved, beyond possibility of question, that the prominences et sist of glowing hydrogen, mixed with oth vapours, also glowing through intensity of bec Janssen, writing of this day's work, says, have lived to-day as in a continued eclipse.

He sent his results to the Imperial Academy Paris, where they arrived two months after eclipse had taken place. A few minutes before. a letter had been read by the President, in whi in seeing the prominence-lines in full sunlig Mr. Lockyer announced that he had sacredst A few words indicating the course of Lockyer's inquiry will doubtless interest reader:

the importance of making preparations for spectroscopic, photographic, and polariscopic observations of the prominences and corona. matter was taken up in good time, and not only by English but by German and French astronomers; and the result was that, though all the expectations which the more sanguine had formed were not fulfilled, the discoveries actually made were so important as to make the Indian eclipse an epoch in the history of solar research. Tennant and the German observers at Aden succeeded in obtaining valuable photographs of the eclipsed sun. These were chiefly interesting on account of the presence on the sun's border of a wonderful horn-shaped prominence, which would seem to have changed very little in form during the whole continuance of the eclipse-that is to say, during the passage of the moon's shadow from the neighbourhood of Aden (the most westerly part of its course), past Tennant's station, at Guntoor, past the East Indian Archipelago towards Polynesia, where it left the earth. We have only drawings, indeed, of the aspect of this remarkable object as seen from the more easterly stations; but as the photographs taken at Aden and Guntoor show a very close resemblance, while the drawings taken further east seem intended to represent a similar structure, it may The invisibility of the prominences at all times, fairly be concluded that during the two hours or so of the eclipse's continuance this wonderful brightness of the direct solar rays. We can, insave during eclipses, is not due merely to the prominence changed very little, if at all, in figure. deed, get rid of these altogether, yet the It was npwards of 80,000 miles in height, and if prominences will remain invisible. For we can we had since had no other means of studying the readily hide the solar image with a dark circular prominences we might fairly have been led to screen inside the eyepiece of our telescope; or conclude that such permanence of figure is charac-we can cause the sun's image to fall on a screen, teristic of these objects. We shall see presently, and then by removing the corresponding portion of however, that the prominences exhibit singular the screen we can get rid of the whole image varieties as respects the rate at which their forms that is, of all direct sunlight. The Astronomerand dimensions alter. Royal has tried the latter of these plans, receiving the sun's light through a circular hole in a screen, Tennant, at Guntoor, Lieut. Herschel, Janssen, prominences did not become visible. The reason 'quenching it in a black bag"; yet the Rayet, and other observers were prepared to study is that the atmosphere is illuminated very strongly of hydrogen could be recognized in the case the corona and prominences with the spectro- by the sun's rays, and this illumination is more this far-distant orb, might it not be possib scope. This was the first occasion on which the than sufficient to obliterate the prominences. to recognize the existence of glowing hydrog powers of this instrument-the most powerful We may reduce it by darkening glasses, but we in our own sun? I remember well a convers means of scientific research as yet devised by reduce the light of the prominences pari passu. tion I had with Dr. Huggins at that time in man-had been applied to the study of the phe- Whatever contrivance we adopt for simply which this idea was discussed by him as obviously nomena presented during a total eclipse. It was diminishing the quantity of atmospheric light, suggested by the observations he had made. His possible that in a few moments problems which must equally affect the light of the prominences, instrument was not, however, well calenlated for ad perplexed astronomers and physicists for and, therefore, we cannot by such means cause pursuing this promising line of research, its dis many long years would be fully explained. If these to become visible. when the light of a prominence was received on persive power having been expressly limited to the requirements of stellar and nebular obserthe slit the prismatic battery spread it out into a rainbow-tinted streak, it would be known that the prominences probably consist of incandescent solid or liquid matter-not necessarily continuous, but, perhaps, in some such form as those solid particles which probably form our cirrus

But we have now to turn to observations of far greater interest and importance.

and "

But when it is known that the light of the

"O. F." might have added (let. 921) the opinion of

:

When Dr. Huggins had analyzed the light the star which blazed out suddenly in the c stellation of the Northern Crown in May, 1 and had shown that the increase of the star brilliancy was due to an outburst of go hydrogen, those familiar with the principles spectroscopic analysis recognized a signinca in the observation other than that which appeared so to speak, on the surface.

vation.

If the bright lines

Mr. Lockyer, already favourably known for Professor Tyndall to that of Sir John Herschel, respect his telescopic observations of Mars (where I have ing the existence of vesicles of water in cloud or mist. by the way assigned him large territories) sd Tyndall considers that the forms assumed by snowof water instead of minute drops had been frozen. crystals are not such as would appear if minute vesicles the sun, conceived the idea of a systems spectroscopic survey of the sun; and in a paper

1

read before the Royal Society in October, 1866, in which he described the advantages likely to result from such a survey, he suggests the idea that possibly the spectroscope might give some traces of the prominences, otherwise only visible during total eclipse. It does not appear whether he intended to examine the disc itself (as Dr. De La Rue had before proposed) for such traces, or round the edge of the sun. Probably the latter, because Fr. Secchi, in a recent paper on the subject, says he was deterred from a survey of the limb which must have proved successful by the announcement that Mr. Lockyer had (with the means then at his disposal) been able to discover nothing remarkable there.

In response to Mr. Lockyer's request a grant was made by the Royal Society, and the construction of the instrument was placed in the hands of the late Mr. Cooke. After some delay, occasioned by the death of that eminent optician, the construction of the instrument was entrusted to Mr. Browning, who completed the work most successfully. It seems that delay occurred before the instrument was finally ready for use, because Mr. Lockyer ascribes the fact of his being anticipated by the eclipse-observers, to "the delays of instrument makers." Who these instrament makers were does not appear. Probably Mr. Lockyer refers to persons to whom he entrusted changes or additions having to do with the telescope, clock, or observatory arrangements. Certainly the skilful optician who made the spectroscope must not be classed with the disparaged "instrument makers," as he is able to demonstrate that though delays occurred while the instrument was in his hands they were not such as he had any control over.

But at length the instrument was ready for work, and in a very brief space indeed it did the work required of it most effectually. Its great dispersive power enabled it to so thoroughly reduce the light of the atmospheric spectrum that the prominence-lines could be quite easily seen, and their places determined. And, as we have seen, about two months after the Indian eclipse Mr. Lockyer was able to announce his success. There has been a good deal of discussion about the share of credit which should be assigned to Janssen and Lockyer severally in this matter. It seems perfectly clear, however, that each should have just the same degree of credit that he would have had had he alone effected the work. Mere priority is nothing in such a case. The only matter to be considered is, whether the two observers independently effected the discovery; and about this there can be no question. But I cannot here go quite so far as to say that the credit of discovering the gaseity of the prominences should be in part ascribed to Mr. Lockyer. Here priority and the independence of the observation are both against him. Had he discovered the gaseity of the prominences, during the interval between the actual discovery and the arrival of the news in England it would have been absurd to mulct um of any share of the credit merely on the score of priority. But as the discovery was announced in England fully two months before Mr. Lockyer's observations were made, it really does seem inadmissible to claim any share of the credit for him.

ones; in other words, that a layer of pro- But perhaps the greatest triumph of observa-
minence matter surrounds the whole surface of the tional skill as yet achieved is to be found in the
sun. Not knowing that this fact had already work of Professor Respighi, who has published
been discovered, he gave a name to this layer, daily pictures of the solar prominences all round the
calling it the chromosphere. Strangely enough he edge of the sun's disc. I have before me as I
regards this layer of prominence-matter,-a layer write the series for January, 1870. There is a
as unevenly bounded as a bed of cumulus clouds,- row of prominences for every clear day, and it
as the true solar atmosphere. That it is gaseous is only necessary to conceive each row bent
cannot be questioned; but so are the pro- round into the form of a circle, and that circle
minences; yet we do not regard them as forming occupied by the dise of the sun, in order to
an atmosphere. It seems to me altogether more picture to oneself the condition day after day
probable that the chromosphere consists of of the great central luminary of the planetary
smaller prominences, and of prominence-matter system.
which has descended after being erupted to great Such is a brief sketch of the progress of re-
heights.
search into the appearance of the solar promi-
Yet more strange is Mr. Lockyer's notion that nences and of the layer of coloured matter whence
the chromosphere, whose well-defined border has they appear to spring. I have been perforce
been seen in so many eclipses, and which has been compelled to leave almost untouched the in-
described by the Astronomer Royal and others as teresting evidence bearing on the condition of
the sierra, and as resembling a low table-land, these strange objects as respects pressure and
really extends far above the limits indicated by temperature; because properly to treat that
the short bright lines he sees all around the limb, branch of the subject would require much more
and in fact to a height twice as great as that of space than is now at my disposal. Perhaps on
the prominences. That some atmosphere the some future occasion I may separately treat of
real solar atmosphere, I should say-extends this matter.
above the highest prominences is obvious,
because the prominences have been seen by
Zöllner and others, slowly subsiding-obviously
against a resisting atmosphere-towards the solar
surface. But the chromosphere is as definite in
all its characteristics as the prominences; and
to any one familiar with the history of eclipses, the
distinction drawu by Mr. Lockyer seems alto-
gether unwarranted by the evidence.

MOUNTING FOR THE MICROSCOPE
BY "ACHROMATIO."

CHAPTER IV.-PREPARATION AND MOUNTING OF
VEGETABLE OBJECTS (Continued).

2.-SOFT VEGETABLES.

(OFT vegetables afford almost any number of

But now a far more important discovery has to Sobjects, by far more than woods, and the be dealt with. The prominences so far had been two together give enough work for a man for felt not seen. It was only by a tedious and unsatisfactory process that the true figure of a some years, if he study botany with the microscope. But if botany is not to be followed prominence could be recognized. Many astronomers were considering whether by any means up by the microscopist, a comparatively few prethe prominences could be actually discerned. Dr. Parations will be quite sufficient to give a general idea of vegetable formation. Besides the sections Huggins, notwithstanding the relative weakness of his spectroscopic apparatus (so far as this of soft vegetables, there must be preparations of special line of research was concerned), succeeded dissections, and from the varying textures, conin mastering this problem, the most important of to use different media and modes of preparation. stituents, and formations, &c., it is necessary any perhaps which, since the invention of the Hence it is seen that botanical objects take time telescope, has been dealt with by the students of and care in preparation. The usual number of solar physics. Using an open slit, and supple-sections should be taken of one subject; but here menting the small dispersive power of his instrument by the use of coloured glass, he, first of all the question presents itself, by what should the mankind, saw a prominence when the sun was not eclipsed.

Mr. Lockyer, so soon as he heard of Dr. Huggins's success, applied the same method. He found that with the powerful instrument made by Mr. Browning he could dispense with the use of coloured media, the prominences being easily seen with the open slit alone.

sections be taken?

If a mere general idea of vegetable formation is wished for, a sharp razor will answer our purpose, but if there is any likelihood of the microto make a cabinet of vegetable objects, I should scopist taking up botany as a study, or if he wishes this instrument there are various forms, the best recommend him to get a Valentin's knife. Of being the one fitted with two thumb-screws for instead of a sliding tapered piece of steel. In the

regulating the distance between the two blades

former, the construction allows of the blades

being kept parallel with one another, as far as construction does not allow of this almost necan be judged of by the eye; in the latter, the

This instrument, of

the former construction and of the best make, about 10s. 6d.; though some makers charge more costs, in case, 15s.; of the latter construction, for it than for the former. If the knife has graduated milled heads for measuring and fixing will be mulcted in two or three shillings more; upon the thickness of the section, the purchaser mitted it was only meant for amateurs with more for, as was explained to me the other day, "it was a special article ;" and although they admoney than wit, still "they sold, and so it didn't

Zöllner, the eminent German physicist, made a series of systematic observations on this plan, and was thus led to important conclusions respecting the physical condition of the sun. Regarding the prominences as indicating the action of eruptive forces, by which masses of imprisoned gas are suddenly belched forth from beneath the uppermost layers of the sun's photosphere, hecessary arrangement. estimated the force requisite to produce the observed effects, and thence deduced the pressure and temperature of the region whence the prominences are projected (see my translation of his I think it was this feeling which induced the paper in the last volume of the ENGLISH MECouncil of the Astronomical Society to decline in CHANIC). Without admitting that the reasoning 1868 and 1869 to assign the gold medal to Mr. is absolutely unimpeachable, which indeed of observation on which he had entered could to his results as full of interest, and affording a Lockyer. Doubtless many felt that the course Zöllner himself does not assert, I may yet refer scarcely fail before long to give him a valid title real indication of the wonderful physical condition to the medal. And this has in effect happened; of our great luminary. He finds for the pressure insomuch, that for my own part, I should think within the region whence the prominences are an injustice done him, were the medal still re- erupted, the inconceivable intensity represented fused; though nearly every one will, I think by 4,070,000 atmospheres; and he calculates that agree with me, that as the late Dr. Miller re- at a depth relatively so small that the most ceived a medal at the same time as Dr. Huggins, powerful telescopes would scarcely render a cor80 Dr. Frankland, to whose skill and experience responding arc on the sun's disc perceptible, the Mr. Lockyer's recent observations owe so large a pressure must be so great that even such a gas proportion of their value, should be associated as hydrogen can only exist in the state of a glowing fluid.

with him in this matter.

had been

was the

matter to them."

little practice; but attention to the following To use the Valentin's knife requires some little particulars will be found to greatly aid the

uninitiated.

which it is desired to cut a section is large, as i In the first place, where the vegetable from the case of a potato, &c., a piece must be cut out from it, according to the sort of section required, of not more than in. in breadth, but of any It was now possible to tell whether a prominence exists at any time on any part of the sun's edge; Secondly, gash the cut-out piece with a *He says he was "not aware that such an envelope height. and by taking a series of line-views (so to speak) after dwelling on the "ideas," "suggestions," and on by the Valentin's knife, so that a slice being suggested by previous observers," and knife, about lin. from its top, or part first acted to determine the shape of a prominence. It was "surmises" of Swand, Grant, Von Littrow, Lever- taken off shall be lin. long by in. broad. Upor much as though one were to look at a distant rier, and Secchi, he remarks, that he mountain through a chink, and by combining a first who gave "experimental proof of the truth the top of this prepared piece of vegetable, the heel of these surmises." It is to be feared some of the of the compound blade of the section knife is to be number of such chink-views together, were so to eminent astronomers he names will scarcely think form an estimate of the shape of the mountain. justice has been done them. Grant wrote in 1868 that placed, and then the knife is to be drawn rapidly The plan was somewhat cumbrous-as Sir John the layer is clearly indicated "; Leverrier in 1860, across it with slight pressure. Herschel said, it was becoming sensible of the fact established by the observations made during the prominences, not seeing them; still it was the totality in the eclipse of this year;" Secchi, that these best that seemed available at the time. Applying subject. These are not surmises; nor is it possible to 'furnish indisputable evidence on the it, Mr. Lockyer found that all round the sun pro-give experimental proof of views founded on the actual minence-lines could be seen, though but short visibility of an object.

"the existence of a bed of rose-coloured matter is a

observations **

In this manner,

dimensions and in thickness according to the a section ought to be obtained of the above arrangement of the blades of the section-cutter.

This interesting plate is the sixth coloured plate illustrating my book on the sun.

It is better to use water with the knife, dipping the latter into it after each cut; and where the operator has not had previous experience, the blades of the knife should be put, to begin with, moderately apart; the distance between them being gradually lessened until a point is arrived at, at which either the skill, or rather want of it, of the operator, or the nature of the vegetable, will not allow of a thinner section being taken. The section may be floated out from between the blades by shaking the latter under water. If the section refuses to come quite out while under water, it may be seized with the forceps and drawn out, the force required for this being in the majority of cases insufficient to tear the section. Where a razor is used, great care must be taken to get it of sufficient sharpness, and while it is in actual use it should be frequently stropped.

Beyond these no directions are required for its as "mother wit" will dictate the actual modus operandi.

use,

The cut sections can be mounted in a variety of ways-in balsam, as well as in gelatine and media of like nature. As full directions for the nse of different media considered best for the different objects would occupy too much space, I must content myself with giving directions for the preparation of those advantageously manufactured at home, and giving a few hints as to the choice of media in relation to the requirements of different classes of objects.

The following recipes are taken from "Le Microscope, sa Construction, son Maniement, et son Application aux Etudes d'Anatomie vegetale," by Henri van Heurck :—

Chloride of Calcium.-One part of the chloride to three of distilled water; to be filtered and kept in a stoppered bottle. This solution is used for transparent objects.

Glycerine. Undiluted, and of the very best quality. Used for slightly transparent objects, and for fecule which alter in the solution of

calcic chloride.

Camphorated Water.-The author of the above

a

work says, "It is the only medium which I have found to preserve the delicate chlorophyle spirales found in certain algae, such as the Spirogyra. These spirales are destroyed in every other solution." To prepare camphorated water, we take flask half filled with water, and drop into it three or four drops of camphorated spirit, and shake violently; this is done for a certain number of times, until a pretty considerable quantity of camphor, in powder, floats. The liquid is then filtered and preserved in a flask securely stop pered.

Fine Oils.-M. Heurck recommends fine watchmakers' oil in preference to essential oils, claiming for it, justly enough, the advantage gained by being able to use with it the ordinary black varnish, and the ease in which preparations may be made with it. It is used for such objects as pollens of plants. The reader must deduce, from the general effects of the preparations appended to each of them, the fitness of any one preparation for a given object.

All vegetable dissections should be carried on under water, illuminated by the rays of a lamp condensed by means of the usual condenser, or a round flask filled with water and suspended from some convenient stand. The water can be held in any small-sized flat vessel, a saucer answering very well. The spiral vessels and fibres should be "teased" out with fine needles, and afterwards mounted in the camphorated water.

When it is wished to put up the petal of a geranium as an object, the epidermis alone should be mounted on the same slide. It may be easily peeled off by scraping up a small piece with a knife, and then stripping by means of the forceps. It should be floated on to a slide, as much water

of

GEOLOGY IN RELATION TO
AGRICULTURE.

II-CAUSE OF THE DIVERSITY OF
SOILS.

charis. The former, a native of Italy, may be
purchased at the aquaria dealers in St. Giles,
Holborn, London, for sixpence a root; and the
latter, an American importation, may be obtained PART
in almost any English river or pond. The best form
of vessel for growing the Valisneria in is a tall glass
jar, such as is used in the chemical laboratory stricts, therefore, is no longer obscure
HE cause of the diversity of soils in diferen
for washing bulky precipitates in. The Anacha- If the subjacent rocks in two localities differ, the
ris may be grown in any shaped vessel, a glass soils met with there are likely to differ also, a
pickle-jar for instance, or if wished in the same in an equal degree.
jar with the Valisneria, but in this case care
must be taken to thin it out occasionally, as
from its more rapid growth and harder constitu-
tion it easily kills its companion.
The Valisneria must be kept in the house in
winter-in a room with a fire is not necessary,
though it greatly aids the growth of the plant.
The Anacharis can be grown in the open air in
summer, and it will live through the winter in the
same situation. To prepare the aquarium, first
wash either loam or common garden mould until
the washing water becomes clear on standing a
few hours, and cover the bottom of the aquarium
with this prepared mould to a depth of from one
to two inches. The plants are now to be placed
in the mould, and the surface of the latter is to
be afterwards covered with half an inch of washed
silver sand, which may, for the sake of appear
ance, be covered with fine pebbles. The water
may now be poured gently in from a small can by
placing a stick inside the aquarium, leaning
against the glass, with its lower end standing on
the pebbles, and pouring the water on to the
stick, and allowing it to flow down it.

When the sediment has quite settled, several fresh-water snails must be put in to keep down conferva, and to devour the rotten weeds as soon as they are formed. If the number of snails is nicely adjusted the aquarium will be kept free from decaying vegetable matter, and consequent putrid fermentation, which necessitates a thorough clean out, while the vigorous parts of the plants will not suffer from the appetite of the scavengers.

By using a large aquarium, fish, reptiles, &c., may be kept, increasing the interest felt in it, and without detriment to its plant-growing qualities; indeed, whether for the microscopist or not, an aquarium creates at once an interest and a study, and if to the ordinary interest of an aquarium the breeding of such reptiles as frogs and lissotritons (newts, effets, efts, &c.,) is added, during the early parts of the year and through the summer, and even into the autumn, the aquarium will afford an endless field for investigation with the microscope.

But why, it may be asked, do we find the sol some countries uniform in mineral character and general fertility over hundreds or thousands field to field-the same farm often presentia square miles, while in others it varies from many well-marked differences both in minera character and in agricultural value? The chief cause of this is to be found in the mode in which the different rocks are observed to lie, upon or by the side of each other. Again, most peu, 2 are familiar with the fact that during periods of and overflow their banks, they not unfrequently long-continued rain, when the rivers are flooded bear with them loads of sand and gravel, which they carry far and wide, and strew at intervals over the surface soil.

So the annual overflowings of the Nile, the Mississippi, and the river of the Amazons, gradually deposit accumulations of soil over surfaces of great extent, and so also the bottoms of most lakes are covered with thick beds of sand, gravel, from the higher grounds by the rivers which s and clay, which have been conveyed into them

into them. Over the bottom of the sea, also, the

ruins of the land are spread, torn by the wares
from the crumbling shore, or carried down from
selves in the sea, and form beds of mud, or bank
great distances by the rivers which lose then
of sand and gravel of great extent, which cove
and conceal the rocks on which they lie.
On these accumulations of transported mate
rials a soil is produced which often has no res
tion in its characters to the rocks which cover the
country, and the nature of which soil, therefore,
a familiar acquaintance with the rocks on which
it immediately rests would not enable us to
predict.

1. Geologists distinguish rocks into two classes, the stratified and the unstratified. The former are found lying over each other in separate beds or strata, like the leaves of a book when laid of its side, or like the layers of stones in the wall of a building. The latter the unstratified rocksform hills, mountains, or sometimes ridges of

mountains, consisting of one more or less solid For this breeding of frogs and newts, nothing mass of the same material, in which no layers or makes a better aquarium than a half butter-tub strata are usually anywhere or distinctly percep (price 6d.) sunk into the ground in the garden, tible. Thus, in the following diagram (No. 1) and fitted up in the manner described, with the necessary addition of the sexes of the animals, the breeding, &c., of which is wished to be watched.

N° 1.

A and B represent unstratified masses, in con nection with a series of stratified deposits. C, D, E, lying over each other in a horizonts! position. On A one kind of soil will be formed, on F another, on B a third, and on G a fourth, the rocks being all different from each other.

By the above means in the early part of this year I bred from five frogs and innumerable tritons, and I was so lucky as to see the exudation and simultaneous fertilization of the ova of the frog on two different occasions, and during the time of pregnancy of the female frog I saw sufficient to make me deeply regret the want of time which prevented a close investigation of the obscure phenomena attendant upon the propaga- If from A to G be a wide valley of many miles tion of this reptile. I should like to hear the ex-in extent, the undulating plain at the bottom of periences of any of our readers on this subject, the valley, resting in great part on the same rock and if any of them should wish for further par- D, will be covered by a similar soil. On B the ticulars in expectation of the approaching season, soil will be different for a short space; and again I should be most happy to supply them. How- it will differ at the bottom of the valley F, and on ever, apologizing for my digression from the sub- the first ascent to A, at both of which places the ject immediately under discussion, I will close this rock E rises to the surface. In this case the chapter with a hint or so on the examination of stratified rocks lie horizontally, and it is the the Anacharis and Valisneria. undulating nature of the country which, bringing different kinds of rock to the surface, causes a necessary diversity of soil.

The circulation of the Anacharis alsinastrum

as possible soaked up with a camel's-hair brush, is best seen in the elongated cells round the
and then allowed to thoroughly dry; after-margin and along the midrib of the leaf. The
wards it may be mounted dry in Canada balsam, skeleton of silica of the leaf may be seen by de-
or in one of the gelatines (glycerine gelatine in composing the vegetable envelope in a boiling
preference, as Deane's destroys the colour), or solution of nitric acid (one part water to one acid).
even in all three.
After cleansing the silica framework it may be
examined with the polarizer. To view the circula-

In gaining even a general idea of vegetable

T. JONES.

THE POST-OFFICE AND THE TELE-
GRAPHS. +

physiology, it is necessary, not only to be ac- tion in the Valisneria, the leaf must first be split. Nown into working order with the telegraph

quainted with the arrangement of the component cells, but also with the circulation of the plant, and as this circulation is best seen in one or two water plants, the microscopist, for their thorough examination, is obliged to keep an aquarium.

This necessity I hope will prove so far an excuse as to warrant my dragging into these chapters on "Mounting," a few hints on the keeping of aquaria. The two best weeds for the purpose of the microscopist are the Valisneria and Ana

It can then be examined in the ordinary way.

that the Post-office has fairly settled system, and is rapidly extending the wires throughout the length and breadth of the land, it

OPAL GLASS. The artificial sulphate of baryta, may not be amiss if we endeavour to give an ex-
when mixed with silicate of soda and spread on a sheet
of glass, gives it a beautiful milky appearance. After a
few days, it will form with the silicic acid, which is
liberated, a perfect combination, so that even hot water
will not affect it. When this glass is exposed to a
higher temperature the film will be changed into a

beautiful white enamel.

That is, containing the same general proportions of sand, clay, lime, &c., or coloured red by similar quantities of oxide of iron.

For the use of the blocks to illustrate this article wa are indebted to Messrs. Lockwood & Co., the publishers of the "Handbook to the Telegraph."

In the Morse printing instrument the message is conveyed by a series of dots and dashes, which, by a variation of arrangement, are made to designate the whole of the letters of the alphabet. These dots and dashes are impressed in a continuous line on a narrow slip of paper, and are read off and transcribed by the receiving clerk. By this means a record of a telegram is kept in the exact state in which it was sent. The signals are produced by the action of an electro-magnet, which attracts an armature carrying a lever. At one end of this lever is a point or "style" which impresses on a strip of paper, moved by the agency of clockwork, the dots and dashes" that spell out the message. The signals are forwarded by depressing the end of a brass lever, either momentarily to produce a "dot," or for a space of time sufficient to produce a "dash." By this means a succession of currents are sent along the line, and the dots and dashes are impressed on the paper at the receiving station, in exact coincidence with the length of time the lever-key at the sending station was depressed. Thus the letter A is represented by --; E by ; T by ; whilst I is designated by "" and M by It will be observed by the attentive reader that, although the message is conveyed in these three methods by the employment of different signs, the alphabet is the same for each instrument. Thus, with the needle instrument, A is represented by one inclination to the left and one to the right; with the bells, it is represented by one blow on the left and one on the right; and with the Morse, by a dot and dash; whilst I is signalled by two inclinations to the left, two strokes on the left bell, or two dots on the strip of paper. This arrangement runs throughout the whole alphabet, the dots and dashes of the Morse corresponding to the strokes on the left or right bell, and to the inclinations of the needle to the left or right.

planation, for the benefit of some of our readers, ( by two strokes on the left, and M by two on the
of the mechanism of the various instruments em- right bell.
ployed by the Post-office in this increasingly-im-
portant branch of the public service.
The telegraph instruments employed by the
Post-office are of six kinds, viz., the single needle,
the bell, Hughes's type-printing, the Morse print-
ing, Wheatstone's A B C, and Wheatstone's
automatic. The A B C instrument is used prin-
cipally in connection with private wires; the type-
printing and automatic instruments are employed
only in first-class offices; whilst the single needle,
the Morse, and the bell are those in general use.
There are, at present, two kinds of single needle
instruments, one with a handle and the other with
two keys, somewhat resembling those of a piano-
forte; the latter of these will, in all probability,
soon supplant the former, and remain the only
single-needle instrument in use. The two keys
are termed the right and left, and the alphabet is
read by causing the upper point of the needle to
incline in one direction or the other as either of
the keys is depressed. Thus for the letter A an
inclination is given to the needle towards the left,
and then one towards the right, represented on
paper thus V. For the letter E one inclination to
the left is made, and for T one to the right; whilst
I is represented by two inclinations to the left, and
M by two to the right. The other letters are
obtained by a variation of the number and posi-
tion of the inclinations to the right and left. The
punctuation marks are designated by a multipli-
cation or a combination of the signs used for some
of the letters, as are also the signals between the
communicating offices. Thus the "period" is
represented by three Is, the comma by three As;
and the intimation that the message is understood,
which should be given after each word, is con-
veyed by the sign for the letter T, whilst the con-
trary is implied by the sign for E. Until recently
the only instrument in general use was the
double-needle, in which the letters of the alphabet
were divided between two discs, and the number
of inclinations imparted to the needle on one or
other of the dials spelt out the message; but
although this was undoubtedly the most rapid of
the needle instruments, and was employed in
transmitting speeches from the Throne and
parliamentary debates, it is not used in the Post-
office system, and, on principles of economy and
accuracy, the single-needle will doubtless soon
supersede it everywhere.

the same room.

The bell instrument is probably the most rapid of non-automatic telegraphs, but is of course not well suited for offices where a number of instruments are in use at the same time and in It consists of two bells of different pitch, known as the right and left bell, and the message is spelt out by the number and variation of the strokes on either or both bells. Thus A is designated by one stroke on the left and one on the right bell; E by one on the left; T one on the right; whilst I is represented

of a lever causing the type-wheel to present one or the other at will. The type-wheel, which revolves continuously, carries by means of bevel wheels a contact-making arm, which travels around the disc of pins acted upon by the fingerkeys. When a key is pressed down the corresponding pin in the disc comes into contact with the revolving arm, and the current is thus transmitted, passing in its course through the magnet, and detaching the armature, which thus comes into contact with a detent. This detent locks a shaft to the train in motion, and when it is released a cam raises the paper against the type-wheel, where it is impressed with the required letter. The current acts in a similar way at the receiving station, by detaching the armature, thus permitting the printing shaft to make one revolution and to take the impression of the letter from the type-wheel, which is brought into a similar position to that at the sending station by means of a detent, which only permits the wheel to start when in unison with that of the sending machine. A feature of great importance is the arrangement by which a maximum effect is obtained from the electro-magnet. In this instrument the armature is held constantly against the cores of the magnet, whilst an adjustable spring tends constantly to draw it away. When a key is touched, the magnetism by which the armature is held is neutralized, and the spring exerts its full power. The armature then rises and strikes against the detent, thus unlocking the printing shaft, which shaft, by means of a cam, replaces the armature in its original position, at the same time taking the impression of the letter. The speed of this instrument is about 200 letters a minute, and its great value, particularly for long submarine lines, is apparent, from the fact of one wave only being required for each letter, and from the simplicity and sensitiveness of the electrical arrangements. The patent rights have been purchased by the Governments of France and Italy for their respective territories; the American Telegraph Company have the right to use it in America, and the sole right for the United Kingdom is now vested in the Postmaster-General.

But perhaps the most ingenious, as it undoubtedly is the most valuable, of all inventions for sending messages by the telegraph is Hughes's type-printing instrument, an illustration of part We have left ourselves but little space to speak of which is here given. It consists of a train of of the other instruments in use at the Post-office; wheels driven by a weight, the speed being it must be sufficient, therefore, to say that governed by a vibrating rod, the free end of Wheatstone's automatic system consists of a which is attached to a crank on a fly-wheel, so perforator, which punches holes in a strip of that its arc of vibration can increase or diminish paper; a transmitting apparatus, into which the according to the amount of force employed. By perforated slip is inserted, and the current sent this means the instrument can only run at the by means of needles which penetrate the orifices speed permitted by the vibrations of the rod; and in the paper; the recording cr printing appaby moving a sliding weight upon this rod two in-ratus, which, by means of pens supplied with ink, struments can be put in motion at a rate almost mark the strip of paper at the receiving station perfectly synchronous, or so near that the differ- with "dots and dashes; " and the translator, will not exceed 1-30,000th of a second in a minute. by the operation of which the telegraphic symbols The type-wheel contains 54 different characters, are reduced to the ordinary characters of the which by a simple contrivance are acted upon by alphabet. The A B C instrument of Wheatstone 28 keys; this result being obtained by arranging is perhaps the most readily understood of any, the letters and figures in two series, and by means and is extensively used by private firms. It con