8ft. would be more free under a parallel lift of pallet; and many makers adopt check-pins to depress the far end, and thus to raise the inner end. If, however, the pallet apertures are judiciously regulated, we prefer a sloping pallet, as conducing to more variety of tone. The rebound of the issuing stream of air will be specially influenced according to the lift of pallet, whether inclined or horizontal, for thereby, as we have shown, quality will necessarily receive modification.

PRACTICAL INSTRUCTIONS IN THE ART
OF DISSOLVING-VIEW PAINTING.
BY SABLE.

Not for self alone was man created.

HEN I was a small boy, with a round face

a jacket

my firm conviction that with a magic-lantern I could go through the world and defy the fickle

and the prospect of a Christmas exhibition was enough to throw me into an ecstasy of delight, which old boys are seldom permitted to experience. But the magic-lantern is no longer the scare-babe of my young days; the rude optical toy for the

this style of painting. I obtained a very beau- from the tube on the glass slab, and a small drop
tiful view of Venice, which cost 15s. 6d., and I of the prepared varnish near it, dip the pencil in
stuck to it until I at length produced a very the colour, and mix with a little of the medium,
good facsimile.
familiar
By this time my hand was and draw the brush on a trial piece of glass, if
surface
with the implements
thankfully I should have welcomed any real member your drawing of two or three inches will
and
on which I had to paint.
the it makes a clean fine line commence the tracing.
assistance; for my books required a master's be magnified eight or ten feet, and you do not
How A steady hand and a good eye are requisite; re-
advice and example. Had the ENGLISH ME- want your lines to look like ragged ropes. In
CHANIC been in existence at that time, I should painting views an engraver's glass is indispensable.
soon have found what I needed; and I assure my Use the turps in the bottle for thinning, but be
friends that in any difficulties they may meet careful to secure enough varnish, or the outline
with they will (with the permission of the Editor) will "work up" in colouring. The lines must be
questions may be briefly and plainly put.
always have my ready help. I ask only that fine in the light parts, and stronger in the shades;
unless this is attended to a good effect cannot be
produced. Examine your tracing brush carefully,
cut off any stray hairs close to the ferrule; six or
The pencil should be thus pointed a
they should all meet the surface of the glass to-
seven hairs are sufficient to form a point, and

THE OUTLINE.

should be kept
to save time and trouble, therefore a look-out
A 3in. circle is the most useful size; it is well

magnifying glass.

them;

display of the frightful and grotesque. It is now the most pleasing portion. Should the foreground outlines of Figs. 3 and 4 there is good practice for

a high-class scientific instrument capable of entertaining and instructing persons of all ages

from seven to seventy.

FIC, 3

which a pretty view 3in. in diameter can be made without "reducing :" fine wood engrav-mended-e.g., Indian ink, chalk, the steel pen, goddess herself. There was magic in its name; views from the vignettes at the head of local &c., but I have given the one with which I have Many elements of outlining have been recomings are good. I have made many of my best note paper, but often a picture comes under no- succeeded best after a patient trial of all. Should tice which will repay the trouble of making a re- any of the lines be thick or ragged do not touch duced outline. take a pair of compasses armed with a pencil, my next paper I will tell you how to apply the A small picture being selected, finish the work and put it aside to dry. In and strike on it a 3in. circle, which will include colour and remedy such defects. In making the circle so as to throw them as near the centre be occupied by any prominent objects, arrange as the view will permit. Next render some tissue paper transparent by means of a little oil, and wipe it quite dry, gum the corners and lay it smoothly on the engraving; if the latter be strong and dark it may require another piece of oiled paper; the use of this is to soften the lines of the engraving and enable the artist to see distinctly the tracing he is making, which he could not do if nothing were laid between the glass and the picture to be copied. The glass circle must be cut from thin "flatted crown," without blemish; three places at the extreme edge, and lay it upon clean it thoroughly, put a little gum in two or the engraving exactly on the circle, which will be plainly seen through the oiled paper, press gently subject be altogether too large to be treated thus, a month. until dry enough to prevent shifting. Should the the artist must reduce it to a correct outline for each. himself, and place this under the glass as pre- and work downwards; this will prevent the A separate glass is to be used for Commence at the top left-hand corner, viously directed; if his outline be properly made, one piece of oiled paper will suffice to soften it.

and varied collection.

to the work, and at the same time to save the re-
A great point gained is to familiarize the hand
sult of one's labour. The "comic " supplies a
good means of doing this, as coarse outlining, which
would be ruinous in high-class painting, does not
so much signify in the grotesque. It would be as
well to procure two copies of this journal, as
this will enable the student to avail himself of the

outlines the kindness of the editor permits me to
offer without spoiling his volume.

flatted crown

Most of us have our recreative pursuits, and if they do not deprive other creatures of blessings which we prize ourselves, they are commendable indeed; but if our enjoyments be diffusive, and gladden other hearts, and light up the faces of others with bright smiles, then they are most excellent. Such a pastime I will do my best to place at the disposal of all who may be able to cultivate this fascinating social art; and if it affords them the pleasure it has afforded me, I have no other wish in connection with it. And I here invite our able optical and chemical contributors to give their aid; they can tell us how to construct cheaply the most efficient form of apparatus, the best and cheapest method of making the appliances and the gas, &c. Quite as wide a field is presented here for the inventive power and ingenuity of the optician, chemist, and mechanic, as in many other occupations I could name. Magic-lanterns are comparatively cheap, and so are telescopes; but these articles are still sufficiently costly to place them beyond the reach of numbers who could ably use them and appreciate them too. A good dissolving-view apparatus is easily obtained by those who can count their guineas, but I write on behalf of those who sometimes find it not difficult to count their shillings. These observations are equally applicable to the pictures. True they are very cheap, but not cheap enough for all who wish to possess a good painted views maintain their price, and my own Highly finished handexperience forbids me to recommend cheap ones, glass, Gin. by 3in., and having prepared the Take a piece of thin clear " as they always entail disappointment, while the printed outline as before directed, fix the glass former never fail to please, and ensure a delightful over it so as to have one of the Figs. 3 or 4 in evening. These papers are addressed chiefly to those who have already some knowledge of draw-quired for outlining:-A small bottle of pure The following materials are ing, the laws of perspective, light and shade, &c., mastic varnish, some rectified turps, two No. 0 and I regret that I cannot do much for those who long hair red sable pencils in ferrules (Fig. 1), a know nothing of the art; however, I shall have a word or two for them presently. I said that my tube of lamp black in oil, a small palette knife; experience had extended over eight years. I came across a slide in my cabinet a few days ago which tells me that if had named fourteen I should have been nearer the truth; and I advise all beginners to date their slides. They will be guide-posts on the road to excellence, showing what has been done, and what is still to be achieved. Many times was I tempted to abandon glass-painting, disheartened and disgusted with my failures. I struggled with perplexities and difficulties, and no friendly hint ever came to light me on my way. Presently some books on the art were issued, and I thought my troubles were at an end; but it was not so. They were neither lucid nor practical. The authors were divided as to the materials and method; one advocated water-colours, another oils, a third the use of both in the same view. I followed their directions, and my productions were most unhappy attempts. Some hints I did get from these works, but I could not avail myself of them; they were to me like oysters, and I had no knife to open them. However, as I had noticed that the beautiful views from Newton's, Carpenter & Westley's, and other eminent houses, were exeeuted in oils, I applied myself perseveringly to

the centre.

FIC.I

FIC.2

re

two small wide mouth bottles (those for Preston
salts answer well), a penknife (Fig. 2), the point of
which should be thin and kept sharp; a few pieces
of linen rag, and a small square of plate glass for
a palette-this should be fitted into a frame from
which it can readily be removed for cleaning; a
piece of white paper should be placed beneath the
glass to show the colours well. I can recommend
the sable pencils of Barnard, Oxford-street. Put
three parts of mastic varnish and one part of
turps into one of the bottles, and expose to a
very gentle heat for a few minutes to prevent the
mastic "chilling;" into the other bottle put some
turps, and keep both well corked when not in
use; also have a small gallipot at hand to
hold some turps for cleansing the brush; this
should be done every ten minutes, or it will be-
sible to make an even line. Place some black
come stiff and gummy, and it will be impos-

FIG. 4

Miss Prim
Propriets House

possibility of smearing. Make half a dozen outlines of each subject, they will do for practice in laying the colour.

THE BLOWPIPE AND ITS APPLICATION
TO MINERALOGY.
ARTICLE II.

HEN about to make an examination of a

nothing, for the purpose of referring it to its proper position in the mineral kingdom, it is necessary before submitting it to the flame, to make a few preliminary observations. In the first place, then, the inquirer should write down in his notebook all he knows about the mineral under examination, its locality, the nature of the strata in which it was found, and then the result of each test as it is applied. When the examination is complete, if he refer to a catalogue of minerals he will probably find one having the same reactions as his specimen. The labour of consulting a catalogue is not so great as may be supposedgroups or families, each group or family having most mineralogists dividing all minerals into

direct sap is given in Fig. 11. The process is too | The Elements of Practical Perspective. By
complicated to be described in detail in so short ELLIS A. DAVIDSON, author of "Linear Draw-
an article as the present; but it will, perhaps, be ing," "Projection," &c. London: Cassell,
sufficient to say that it proceeds very much in Petter, & Galpin.
the same manner as the other sap, only several
squads of sappers are employed at the same

nature and subdue them to his will. The pro- science classes in connection with the Science instantly tends to return to its normal state: the

over the same sheet of water, what will be the
result?
The movement which will be produced by their
combined action is given in (B).

the tube. We are now in a position to understand
in what the quality of a musical note consists-
simply in the proportion in which the harmonics
are blended with the fundamental tone. Instru-
ments in which the harmonics are very feeble-in It will be observed that the undulatory character
which the fundamental tone is nearly unmixed- is not lost; we have still a wave-movement, but
sound poor and thin. On the other hand, when the a wave-movement with this important modification,
very high harmonics are present in considerable that it undergoes a recurring fluctuation in in
force, the sound is penetrating and shrill. The tensity. At places where the crests of the two
harmonics are, relatively, much stronger on waves conspire [represented in the figure by the
stringed than on wind instruments. They first, third, and fifth dotted lines], the water which
vary very much, even on the same instru- would have been separately raised by each is
ment, according to modifying circumstances. doubly raised by their combined action, and we
Take, for example, the piano. Here much have a wave of twice the height of either. On
will depend upon the way and place the string is the other hand, where the crust of one wave is
struck-everything of the nature of abruptness overtaken by the trough of another [represented in
tending to develop unduly the very high har- the figure by the second and fourth dotted lines], the
monics, which are better absent. Hence the care water which would have been raised as much by one
with which the hammers which strike the string as depressed by the other is consequently left un-
are covered, so as to temper the suddenness of the disturbed.
blow; and hence, also, it is a matter of much import-
ance in the construction to arrange that the ham-
mer shall strike the string at the proper distance
from the end. This can make no difference, of
course, in the pitch of the note, but it sensibly
affects the comparative strength of the harmonics.
Accordingly, it is found that by placing the hammer
so as to strike the wire about one-seventh to one-
ninth of the whole length from the end, the most
pleasing tone is obtained.

The most beautiful and interesting application of this theory of the bearing of the harmonics upon the quality of sound is the explanation it affords of what it is that constitutes the difference between the vowel sounds of the human voice. Here we have an instrument exceeding all others in its powers of adaptation-one in which not only the pitch, but the quality of the note, can be altered at will. It can be shown that the distinction between the utterance of one vowel sound and another consists only in this, that each contains a different group of harmonics blended with the fundamental tone. The rationale of vowel sounds was first given by Sir Charles Wheatstone, and recently the subject has been reinvestigated most thoroughly by Prof. Helmholtz of Heidelberg. The vocal organ belongs to the class of reed instruments. The air, when forced up by the lungs, is driven by pressure through a slit made by two vocal chords. The pitch of the note is determined by the tension of these vocal chords. The peculiar vowel character is given by the size and shape of the resonating cavity formed by the mouth and upper part of the throat. This we can change, from moment to moment, by the movement of the tongue and cheeks. The sound, as it is emitted by the vocal chords, is full of harmonics; and the resonance of the cavity, according to its varying form, reinforces and inten sifies some of these harmonics to the exclusion of the others, and thus determines which of the vowel sounds the note shall assume-whether an A, O,

E, &c.

If this reasoning be accurate, and one vowel sound only differ from another in the relative proportions of harmonics present in the tone, and if no essential element has been overlooked in the analysis, it follows that by artificially combining a system of pure notes to represent these harmonics we ought to be able to construct synthetically a vowel sound. Now this Helmholtz has succeeded in doing. He has arranged a series of tuning forks to correspond to a fundamental note and its harmonics, so that by means of electro-magnets he can make such of them as he pleases sound with more or less intensity, and by mingling their notes in the due proportion he has succeeded in reproducing with very tolerable accuracy all the principal vowel sounds.

Let us now proceed to examine what happens when the same medium is agitated at the same time by two different systems of waves. For our present purpose we may limit our inquiry to the case in which the two systems of waves have nearly the same period, or in other words, in which the separate waves in both succeed each other at nearly the same

intervals.

It will be simpler to investigate this matter in the case of transverse waves (such as those of water), as being more easily represented to the eye.

Let figures A and C represent two such systems It will be seen, on examining these figures, that they have been drawn in such a way that the intervals in (C) are a little shorter than those in (A), eleven undulations in the latter answering to ten in the former. Now suppose that two systems of waves such as are here depicted, separately main tained by different causes, are passing independently

For this, as well as for his other researches in the Theory of Sound, see Helmholtz's most interesting work: "Die Lehre von den Tonempfindungen." A good French translation of it has been recently published.

To apply this to the subject before us. We have a corresponding state of things brought about when two notes of equal force and very slightly differing in pitch are sounded together, only that for waves of water we must substitute successive pulses of the air. From what we have seen, it follows that the result is one system of waves of sound with recurring fluctuations, i.e., one musical note with recurring reinforcements and abatements in its intensity.

Such is the account of the phenomenon familiar to musicians that when two notes nearly in unison are sounded together a succession of beats is heard.

It is important to observe that the nearer the approximation to perfect unison the slower are the beats. [The beats were here shown by means of organ pipes, tuning forks, &c.]

These beats and the cause of their production have been long well known. Latterly they have, however, acquired additional importance, as Helmholtz has founded on them a solution of the very interesting problem-What is the physical cause of musical harmony and discord-why are certain combinations of notes pleasing and others painful to the ear?

A is a round vessel, about the same height as its diameter, with a stout wire around the top edge; this to contain the water to be distilled.

B is the condenser cylinder, made at the bottom with a shoulder and flange to fit easily into the top of A; the flange runs up a little above the shoulder, as shown in the sketch.

The condenser, B, is also filled with a cone c (like the top of a funnel inverted), and tightly soldered at its base, near to the bottom of B; leaving height enough, however, to insert anywhere on the circumference of B the little short tube s. The condenser has no top.

Now to use. Fill A two-thirds with water; put it over your gas (or any other) stove; when the water boils, put on the condenser, B, and fill the upper part with cold water: the steam as generated strikes the cold surface of condenser c becomes condensed, and trickles down to the trough at the base, and soon flows out of the short tube, e, pure and sweet; ƒ is a detached tube, which slips on and off s, and serves to conduct the water where desired.

This simple affair will distil for hours, even after the water above the condenser has become quite warm (of course it works faster to change this occasionally, pouring part back into A, to make up for the loss by evaporation). It will prove a blessing to many a photographer, and, I may add, it is not patented.

A great advantage that this machine has over all others is, that every part can be kept perfectly clean and with little labour.

His explanation is a very simple one. When two notes are almost exactly in unison we hear slow beats; as the interval is increased the beats quicken, till a point is reached when they become too rapid to be separately counted, but yet are plainly perceptible in the roughness or want of continuity they impart to the tone. It is this roughness which produces the jarring discordant effect upon the ear. At first sight it would seem as if we could only thus account for the discord produced by two notes ON THE ELECTRO-DEPOSITION OF COPPER very close together in the musical scale, say differing by a semitone, and that we left other discords unexplained.

It is to be remembered, however, that we have shown that each musical note is accompanied by a suite of harmonics. In considering the result of the combined action of two such notes, we must not therefore confine our attention to the fundamental tones, which indeed may be so far apart that they may produce no beats to affect the ear, but have to consider all possible combinations of the fundamental and harmonics of the one with the funda. mental and harmonics of the other.

For example, take two notes, differing by an interval half a tone less than that of a perfect fifth. Here the second harmonic of one, which, were the interval perfect, would precisely agree with the first harmonic of the other, as it is, does not coincide, but is just near enough to give rise to the roughness already mentioned.

AND BRASS.

BY W. H. WALENN, F.C.S.*

TT T is intended in this paper to put forward the

present condition of the electro-deposition of copper and brass, with sufficient reference to the history of the subject to make comparatively recent improvements well understood, but treating the process in a practical manner, and with reference to some improvements and manipulations that are adopted by the author.

Mr. Alfred Smee, in his "Electro-metallurgy," deposition of copper from acid solutions as well as dated 1851, gives much attention to the electrofrom neutral salts; and he alludes to potassic cyanide as a menstruum for dissolving the copper when articles of iron are to be submitted to the coating process. In mentioning the cyanide electrocoppering solution, Mr. Smee does not notice the deposition of reguline metal. In reference to the fact that hydrogen gas is evolved during the electro-deposition of brass, he has a chapter (length five pages) upon the reduction of alloys, in which he states that zinc and copper have been reduced contemporaneously, and their union afterwards been informed of Professor E. Davy's discoveries effected by heat. Mr. Smee has evidently not in 1830 (see Phil. Trans., vol. cxxi., pp. 147-164), C. V. Walker in 1845. Certain patented inventions or of the labours of M. De Roulz in 1841, or of Mr. also refer to electro-brassing at this early date, e. g. Fontainemoreau's invention, No. 10,282, A.D. 1844; De la Salzede's process, No. 11,878, a.d. 1847; Fontainemoreau's plan, No. 12,523, A.D. 1849; Russell and Woolrich's discoveries embodied in No. 12,526, A.D. 1849; and Steele's patent, No. DISTILLED 13,216, A.D. 1850.

Following out this train of thought, Hemholtz has drawn out a table of harmony and discord on the following principle. Applying his theory to the violin, he has calculated on a probable system of computation the amount of roughness due to the action of the beats for each interval in the musical scale, i.e., the amount of roughness which would arise from the interference of the fundamental thus arrives at a priori, as to the relative value in tones with all their harmonics. The conclusions he point of harmony of the different intervals, when compared with the verdict of the practical musician, show an accordance which leaves little doubt of the truth of the theory.

A SIMPLE WAY ΤΟ MAKE
WATER.

I

HAVE enjoyed with genuine photographic relish the dialogues contributed to your columns by Mr. Anderson. In general, they announce plain facts, sound sense, and, withal, a spice of genuine wit.

His method of making a still, however, is both expensive and complicated, so I propose here to to give you a sketch of an apparatus for distilling pure water which will perform all that Mr. Anderson claims, at one-tenth the cost, and far simpler. It is not original with me. Some sixteen months ago a man told me about it, and I went over to the tin

He

The point of view, the sphere of thought and the plane of action from which Mr. Smee was led to regard the electro-deposition of metals, was not favourable to the development and classification of facts that were subsequently recognized. had only studied in detail neutral and acid solutions, and these, in conjunction with the physical laws common to all substances, led him to believe that the evolution of hydrogen gas was an evidence of the existence of the metal in the non-reguline form. Doubtless his admirable researches in relation to his Chemico-mechanical battery," involving, as they did, only the employment of acid solutions, tended to confirm his views respecting the influence

of the evolution of hydrogen gas (during electrodeposition) upon the metal obtained. At the present time, however, it is well known that there are solutions which will deposit reguline metal during the copious evolution of hydrogen from the cathode;

this tahes place generally during the electro-deposi

tion of alloys. Many alkalino solutions of single metals also exhibit this peculiarity.

It may be that Mr. Smee's views respecting the evolution of hydrogen from the cathode have unduly biassed him in regard to the theoretical views that he puts forward in his chapter upon alloys. These views will not stand the test of experiment and rigorous examination when alkaline Lolutions are employed. Considerations respecting "the removal of gas" weighed with him, in conjunction with the laws of the conduction of electric force through various media, in the result that he arrived at respecting the electro-deposition of alloys. This result was that alloys might possibly be electro-deposited without the evolution of hydrogen and by means of an "intense voltaic current." Now that alloys are electro-deposited commercially in a reguline form, the scientific man of the present day can look back to the enunciations of Smee with great respect, but as incomplete. The ordinary accompaniment of this deposition is a copious evolution of hydrogen gas from the cathode, and although an intense voltaic arrangement is usually employed, it is partially to compensate for the waste induced by the gas evolved, and to save time in the operation of coating. The author's improvements stop the evolution of hydrogen and enable the electro-motive power to be reduced to that of a single Smee's cell.

Mr. Smee's views have been prominently put forward because they present a definite stand-point, and because the general knowledge of the subject may be said to date from his able exposition of the position of the science as it was when his work was

written.

If first principles are consulted, it will appear that, in alkaline solutions, the proneness to evolve hydrogen gas during deposition arises from the joint action of two causes, one electrical-classified

as such by Mr. Smee-the other chemical. The electrical cause is the small quantity of metal in solution in comparison to the electric power employed: this cause can be lessened or removed by using a solution that contains a greater percentage of metal than that usually employed. The chemical cause is the disposition of the metal of the alkali to go to the negative pole along with the heavy metal or metals, and thus, by being electro-deposited for an infinitely small space of time in contact with them, decomposing the water, thereby getting oxidized, and setting free the hydrogen as a secondary effect; this cause can be eradieated by providing in excess a decomposable compound radicle that will take a certain amount of combined oxygen with it to the cathode, and thus, when decomposed, will enable the hydrogen that would otherwise be evolved to be oxidized into

water.

In the case of brass, a solution containing the cyanides of the component metals dissolved in excess of potassic cyanide, possesses the remarkable property of furnishing the copper and zine to the cathode in such a form that, during deposition, they unite and form a true alloy; this tendency to form a true alloy is increased by the presence of a salt of ammonium, for in connection with copper (especially as cupric ammonide) the gas that would otherwise be given off is replaced by metal, this result being secondary and, in so far, a chemical reaction. It is usually deemed sufficient to charge the solvent solution (the potassic cyanide and ammoniacal salt solution) with brass by electrolysis, but this will be found on trial to evolve gas and to be only workable by two Grove's cells. The author finds that it is practically serviceable, to add to a solution that is charged with not less than two ounces of as it will take up, and then it will probably take brass per gallon, as much of the metallic cyanides still more of the copper and zinc oxides respectively. Should this treatment not perfectly prevent the evolution of gas, the cupric ammonide is added about two or three ounces per gallon. The cupric ammonide may possibly carry the combined oxygen to the cathode; in that case the action may be expressed by the following equation:

At the cathode before chemical reaction.

{Cu2O, 4 NH; +4 H2O} + H2 ·

cupric ammonide

hydrogen

At the cathode after chemical reaction.

Cu2 + 4(NH) + 5(H2O)

copper ammonia

water

When the evolution of hydrogen gas has been stopped by the means above set forth, a single Sinee's cell is suficient to deposit the alloy, thus showing that an intense voltaic current is not absolutely necessary, but that the process requires result.

ON THE USE OF TIN-FOIL FOR PRESERV
ING SUBSTANCES LIABLE TO CHANGE
ON EXPOSURE TO AIR.

Teen cumployed for preserving a great number

IN reduced to thin sheets has for many years

a certain condition of solution to give a perfect
The author prefers to use a menstruum containing of substances from the action of air and moisture.
potassic cyanide and neutral ammonium tartrate in The thin leaves (foil) of this metal are essentially
When cemented to the
equal parts and dissolved in five times their weight repellent to moisture.
of water, to dissolve the brass in. This is then surface of damp walls, they protect the paper.
treated as explained above to prevent the evolution hangings which may be afterwards applied, and
of hydrogen. This solution is employed in conjunc- of boxes and drawers in which dried medicinal
they are in like manner used for lining the interior
tion with heat, and a single Maynooth cell or a leaves and flowers are kept. It has long been the
magneto-electric machine of suitable power. It has
been found, with some electro-brassing solutions, practice to enclose chocolate in tin-foil, to prevent
difficult to deposit, continuously, a given quality of the fatty matter contained in it from soiling the
brass; with this solution the regulation of the Paper which forms the outside wrapper; in the
proportions of copper and zinc in the alloy is made same way butter of cacao itself is preserved, and
by altering the heat accordingly. If the solution is
some sorts of sweetmeats, sausages, and cheese are
kept uniform, as shown by a ready test, it is very pouches are lined with tin-foil to preserve the
among the articles similarly protected. Tobacco
easy to deposit a given alloy at all times.
Before entering upon some practical points con-
flavour and humidity of the tobacco. Cakes of
nected with the electro-deposition of copper and opium are kept in a moist and uniform state by
brass, it will be well to remark that acid solutions wrapping them in this material, and bisulphate of
furnish a spreading deposit matted together, retificial seltzer water with Briet's apparatus. Lastly,
soda is kept in the same way, for use in making ar
sembling the spreading of mortar by a trowel;
whereas alkaline solutions furnish a deposit stand-
on account of the opacity of tin-foil to the rays of
ing up from the receiving surface at right angles light, bottles are coated with it for the purpose of
thereto, as the hairs of a brush stand out from the excluding light from vegtable substances which
brush itself.
would be injured by its action.

In coating wrought or cast ironwork, it is often desirable to coat with copper prior to electro-brassing; the alkaline bath should be employed above the temperature of the air, sometimes 160° Fahrenheit; this method of working promotes the contact of the coating. The article should be well cleaned so as to have a metallic appearance, with a pickle of weak sulphuric acid, scrubbed with sharp sand, washed, scrubbed with a portion of the depositing solution, and then placed in the depositing trough. The electrical connections may then be made and the coating allowed to form for two hours or more. When a sufficient thickness has been obtained the article is washed, and dried in hot mahogany

sawdust.

Notwithstanding the knowledge of all these facts it might be said that the application of tin-foil for still rather limited and there seemed to be a prothe preservation of substances liable to change is spect of its admitting of a more general use than

has hitherto been mode of it. At the same time

there was an absence of any precise experiments for the purpose of determining a in scientific manner the degree of impenetrability of tin-foil. Having been engaged for some time in the investigation of this subject, I have obtained the following results:

For many years past I observed that cacao butter, bottles into which it has been introduced in the which readily becomes rancid even when kept in melted state, if the bottles be opened from time to The tarnishing of the coating increases its beauty moulded in tablets and wrapped in tin-foil. This time, does not undergo the same change when and does not impair the article, for the tarnish is fact, which was confirmed by many observations, not corrosive rust, like the oxide of iron, but is a and could only be explained by assuming the improtective film. Two hours' coating will protect from rust in ordinary indoor work, but the best penetrability of tin-foil to atmospheric air, formed protection from rust (and this is serviceable even in the starting point for some experiments in the damp air) is to give two hours' coating in an alka-same direction, which proved satisfactory. Thus, a line bath, and then let the article remain all night piece of well-burned quicklime, inclosed in a double in an ordinary acid sulphate of copper bath; this wrapper of tin-foil, was exposed to the atmosphere plan utilizes the matted coating as well as the of the laboratory by the side of another similar vertical deposit. If desired, a brass coating may the latter became slacked, that which was protected piece which was exposed without protection. While be given over the last-mentioned copper coating. By suitable mechanical arrangements, the articles by the tin foil, and weighed 92-2 grammes on Decemin the acid bath, and the dissolving plates therein, at the expiration of one month, and after being kept ber 1, 1867, had only gained 3 decigrammes in weight may be moved-preferably by a to and fro movement-during deposition. This treatment shortens until March 25, 1868, it had only increased to 4 the time of the deposit, and makes it (the deposit) grammes. It had thus gained only 18 grammes in four months. On being then taken out of its metallic envelope much heat was developed from absorption of moisture, and it fell into powder. foil for preserving bodies from the action of air and Satisfied by this experiment of the efficacy of tinmoisture, it seemed probable that substances the most susceptible of change might be kept in the same way. It was found that substances so deliquescent as chloride of calcium and liver of sulphur, and efflorescent salts such as carbonate and sulphate of soda, remained almost unchanged when wrapped in tin foil, increasing or diminishing only to a few thonsandths of their weight in several weeks.

uniform.

The roller which is exhibited was treated in this manner; it now weighs 1251b. having 291b. weight of deposit upon it, the coating being 3-16ths of an inch thick. The other works show various applications of electro-coppering and electro-brassing. The price of the above-mentioned coatings, when a single Maynooth cell is used, is 2s. 6d. per lb. of metal deposited. When a magneto-electric machine is employed the cost is much reduced, viz., to 1s. 6d. per lb. of metal deposited.

In con

The coating given by means of the improvements
introduced by the author is superior to that given
by any other known process; these remarks apply
to the economy of the question, also to the solidity,
perfection, and beauty of the result.
sequence of the non-evolution of hydrogen, the
adhesion of the coating to the underneath iron or
other metal is ensured; also the coating is solid and
spongy, as it is when hydrogen gas is allowed to be
compact instead of being more or less detached and
eliminated.

The ammonium tartrate solution used for electro-
brassing, as well as the methods of preventing the
evolution of hydrogen during deposition that are
mentioned herein, form a part of the subject matter
of Specifications No. 1510 (A.D. 1857) and No. 3930

(A.D. 1868).

Other experiments were made of a more precise become rapidly dried and ultimately hard when excharacter. It is well known that fresh lemons posed to the air, and they also become parched and covered with mould. I had endeavoured to prevent this drying and moulding by placing the lemous in Thus, for example, in twenty-one days the lemons close vessels, in dry air, in sand, and also in bran, but none of these methods proved efficacious. lost on an average, 17:33 per cent. of their weight in sand, and 17:13 per cent. in bran. Experiments were made for the purpose of ascertaining the effect of enveloping the fruit in tin-foil, and also of coating it with a film of collodion. Some of the fruit prepared in each way, and some unprepared, was weighed, exposed to the air, and again weighed at lemons and oranges, and the following results were intervals of a month. This method was applied to

obtained.

In two months the lemons had lost 42 per cent. of 1. The unprepared fruit became rapidly dried. their weight, while oranges, in the same time, had

lost 26 per cent.

The uses to which electro-brassing may be applied have yet to be greatly developed. Amongst the rest may be mentioned: the prevention of rust; the giving an improved printing surface to type and electrotypes; coating the poles of electro-magnets for the prevention of the "residual charge" therein; covering rams, plungers, piston rods, rollers, &c., Malaguti and Sarzeau's formula for cupric amwith an adhesive and endurable coating; also monide being used. That is to say, before lining cylinders, pumps, and iron vessels with cop. decomposition or chemical reaction takes place, per or brass. The application of the processes that the whole of the cupric ammonide together with ave been described to many purposes of crdinary the eliminated hydrogen goes to the cathode; after life, such as railings, architectural ornaments, &c., and oranges 22.5 per cent. will exemplify the good results to be obtained by the union of the strength of iron with the beauty of copper or brass.

the decomposition or chemical reaction has taken place, metallic copper is deposited, ammonia is in solution, and water is formed.

In treating the ordinary cyanide copper solution for the prevention of the evolution of hydrogen, the zine cyanides and oxides mentioned in the instance of the brass solution are left out.

the Prussian, 12-36; Austrian, 12-45; Russian, 13.75;
The Spanish foot is equivalent to 11-03 English inches;
Portuguese, 12.96.

2. Collodion, when applied to the fruit alone, exerts but a feeble preservative influence in retardlemons coated with collodion had lost 29 per cent., ing spontaneous evaporation. In two months

3. Tin-foil almost entirely prevents the drying of the fruit. In two months, lemons had only lost 158 per cent., and in three months 3:16 per cent. In one case the loss was only 0.92 per cent. during in two months. Oranges lost about 5 per cent. the longer period. On the removal of the metallic envelope, the fruit was found to be as fresh and