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JULY 15, 1870.)

he English

AND

ENGLISH MECHANIC AND MIRROR OF SCIENCE.

Mechanic

aware of

385

¿ROR OF SCIENCE AND ART. to sit with the weaver of Lyons in the production humiliating to the working class genius of

FRIDAY, JULY 15, 1870.

VALEDICTORY.

time, when more habituated to these rivalries, they | German; the Russian, Spanish and Italian being are of immense, and even immediate nae. We are, hors de concours. kept out of many fields by that rarest of all senti planaibility in all this. Workmen's mechanical ments a national modesty. This point requires schools, no doubt, abound more on the mainland explanation, which we hasten to give. It is a of Europe than in these islands; but we are Now there was a good deal of popular idea, among us, that we can never hope not of silk tissue. Why not? Lyons borrowed her England in the canning from Venice, bays a principal part of her which have taken place. any failure which has been machinery in Great Britain, and imports her raw ns that this is not the real question involved. It material, as we do, from China, Persia, and Italy, is not whether we are outdone by rivals; but international competitions A: Paris, at Amsterdam, at Munich at Wittenberg. whether we might not outdo ourselves as we are, Indeed, it strikes st Leipsic, at Mayence, last year specimens from by what we are capable of being. To that result the English loom were shown which by no eye do these workmen's exhibitions tend, and in that

E following is the farewell address of Dr. could have been distinguished from the finest of prospect we must welcome them. The choral Lawson, late Editor of Scientise Opinion: Frenchmanfacturers. So, too, with porcelain, workman's Bong, sung in Dutch at Amsterdam,

be pardoned, we quote from it one stanza :-
acts forth the ides, and, if a free translation may
No wonder of iron, or gunpowder-fed,

No cancer of steel to whizzing of lead,
Kaxes the Flood in car arteries tingle:
But the whird of the wheel, and the whistle of steam,
And the bathing hiss of the wething stream,
Is the sound where our sympathies mingle-

Various correspondents have kindly expressed with teate, with all the £44, with
regret that the present Editor should cease praises firmwares, and have been in dancer of
been deafened out of self-report by foreign
We have
old the reins of Scientific Opinion. We getting that which in Team'y we
k them for their good feeling. Mach of the have taught to half the world. Not, by any means
ess which has attended our labours has been thus we would counsel ostrést er
to the generous help and friendly advice, nesciasons from
the part of car in the exhibiting; bet a
gestion, and encouragement held out by one who both wing the Of course a Workmen's Exhibition may be in-
respondents, and especially by one who, we French and has ans are a 24. Te tended to serve one of two purposes, or the two
not hesitate to say, is the first man of Science shall recorte, in both, the size of a pear together. It may be designed to meet the many
the age. But, in retiring from the Editora
air, we do so not without a feeling of relief
en if tinged with regret at losing pleasant in a Ergest must trane fe so that his shitty shall exceed that of his rivals
rcourse with many respected colleagues. The it the reis eVOL Bt pris for = bieres to cher natirna. Or, we repeat, it

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rent of politico-scientific questions as to be enabled to help public opinion on its way to reform, is so arduous, so unceasing, attended

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miraculty and home, they become inevitably

so much anxiety, and such intense rest. by Cathed by a band sino work so good has been hat after nearly two years of editorial tol, we ZRT CLEAĆ JE of Fat the Best àme to the Crement as that which has been

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are prepared for DE BER

FTER nearly twenty years of experience it to one episode. In

the De their elevation in the Bucal we

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tically to interest working men in artistic and and the sled neces of de amerian Ceamara de mecatre ar met eri as that of Set industrial exhibibitions, they must makers, building-paris-sa ray baIG I UDA

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and patience wasted upon elaborate parowers domestictT, TO SELL 2011 quilts representing every colour in the dr permairimu na

f the British army, tables and tea-se de ute golden natten
orabining a thousand pieces of wood; asumate shoes drop and

himes, and other monuments of devotion. In They smore AZ EL FIN D
ating a Chinese dexterity and perseverity tina n-
Et not improving either the position & the fins are of a tomato tram at
pacity of the worker. At present we have some the counter a setem
leans of judging how far this or are working men a

stem has prevailed at the Agricultural Hal pertate Te

at there is reason to believe that the emulatin must be the seruan 1 20 ill be seriously and strictly industrial. Its so and his power d @international, as we have said. Now a great with b Blom fficulty has always stood in the way of commu. vol the statis Meation between the artisans of one country wld í vetën date And those of another. The east of travel frizing, HĚDNATA B bstacle. The want of a common language is an en eet te hrane other. The value of time, to people who, by daily. Bunun tala kone effort, earn their daily bread, is a third. Still, thertorte b

our superior working-classes will find, in coarse of respeito to the iron s

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port trade, as es not exhibit as of last year, A the increase of ports in 1869 was or gold, the produce d out last year that returns of imports for

s therefore necessary to returns of both years in comparison with previous e of £12,493,517 for all other inst £12,014,836 in 1868. The year increased from 683,977 to Aue per head of the population 4d. in 1868 to £17 11s. 9d. in se may to some appear unimmust be borne in mind that for 18 have been in excess of d that the changes in the people have considerably

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But at any rate the general result is, that the performance of a reflector must be similar to that of an achromatic in which the centre of the object-glass is stopped out by a patch of a size proportioned to that of the small speculum. Sir J. Herschel says in his book on The Telescope," that the performance of an achromatic object-glass is often very materially improved by a central patch of from 1-12th to 1-10th of its diameter, the increased distinctness much more than compensating for the loss of light. As quoted by Dawes, however, he recommends a patch of 1-6th to 1-5th of the aperture. Dawes himself found the minute companions of large stars sometimes hidden, and the discs of nearly equal stars apparently distorted, when the brighter rings passed through them; and therefore he seldom used the expedient, though admitting that "in some instances it is undoubtedly advantageous." It was also occasionally employed by Admiral Smyth, to increase separating power in the examination of very close pairs. According to the Rev. H. C. Key, one of our highest authorities, the proportional apertures of reflectors to refractors of equal dividing power are as 26 to 31, and this advantage arises of course from the smaller disc given by the former construction.

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one of these industries exists which has not been refers to the article on light" in the "Encyclo- violet matched violet, we should find still that green promoted by the emulous spirit of international padia Metropolitana." Perhaps some of the in the one would not correspond with green in the exhibitions. We would therefore counsel our readers of the ENGLISH MECHANIC who have other, or if we made the greens continuous, the mechanics to take these opportunities in good access to that publication will favour us with reds and violets would no longer match each other earnest, and to appreciate the chances they offer of some information as to this point, which is of con- The result of this "irrationality" is that two lense general and personal advantage. The world siderable interest. formed of these materials cannot possibly pr knows too little of its workmen. Thousands of duce a colourless image. Their contrary dise tasks finished by apt and patient hands, tender sion may be varied in many ways, so as to br. suggestions of form and colour, marks of thoughtdifferent colours to match, but it will be iz ful capacity and memorials of loving care, like that impossible, in the use of these media alone. bestowed by Ascanio on his lily, abound in the include them all in one focal image: one or we workshops whence, hitherto, no name has ever will always be left out, and appear as a surrou issued forth to fame. It is with pleasure then, we ing fringe to any white or luminous object, wh notice that in the forthcoming exhibition which Her is known as the "outstanding colour," or Majesty has privately visited, and the Prince of ary spectrum.' The great art of the optician Wales will open, the personal merits of the workof course so to arrange the balance of co man will be recognized. Indubitably while he tion that the brightest colours shall be com demonstrates his own high quality he will perinto approximate whiteness; and the best ef ceive that he has much to learn from his fellows, considered to be produced when a blue frits s and we trust, notwithstanding our denial of the left outstanding in focus. When this is the idea that foreign workmen are, upon the whole, an object-glass is said to be "over-corrected inferior to ours, he may yet be so unprejudiced as colour," the meaning of which I believe to be the to acknowledge that something may be taught to the correction has been pushed beyond the p him by the Frenchman, the Dutchman, or the in which simply the extremes of the spectrom German. How is it that we cannot make articles would be combined. This blue tint may, however, de Paris? How is it that we are utterly beaten be thrown out to an unpleasant degree, and . in toy-making by the manufactories of Nuremburg? said to be usually so in the Munich glass This localization of peculiar industries is among The result of course is that the whiteness of the most unintelligible of phenomena. A workfocal image, being impaired by the absence of the men's exhibition brings it however before the blue, exhibits the complementary tinge of a faz workman's eye, and sets him reflecting upon his orange, which becomes visible more especially position in the great race of industrial nations. the use of high magnifiers. When the correc At an exhibition he can see clearly on what courses, of the brightest colours is as complete as cu and for what prizes, he is first, second, or third, or not effected, Sir John Herschel says that the ins placed at all. We have every confidence in the of a white object will show a purple or E prowess of our exhibitors at the Agricultural Hall, fringe (which has sometimes been compared but would prefer that our mechanic should look the hue of claret) on one side of the focus, an to the exhibition less for triumph than for green fringe on the other. Attempts have be teaching. made, with more or less success, to get rid of the nuisance, which involves not merely an un pleasant effect to the eye under high powers, but a loss of valuable light. Dr. Blair succeeded admirably by means of fluid media, but the idea has dropped into what seems undeserved oblivion. Wray has attained the same end, in what may be a more permanent mode, by the interposition of a trans parent current between the lenses; but his instruments are as yet not generally known. It is more to our present purpose to remark that in a perfect object-glass another defect requires compensation, as well as that of colour, the spherical form in which alone lenses can be well worked producing, alike in theory and practice, a shorter focus for the rays near the edges than for those in the centre. This defect, which is calei spherical aberration, or spherical error, or some times aberration only, admits fortunately of bein neutralized, at the same time that this dispersion is corrected, by the combination of two lenseshappy circumstance, which makes the achromatic object-glass a truly wonderful work of art; the compensation is, however, frequently imperfect in practice.

HINTS TO ASTRONOMICAL STUDENTS.

(Concluded from page 265.)

This then is one great difference between the definition of equally perfect reflectors and achromatics (supposing, in the case of the latter, that the disc and rings have the same magnitude and proportion that they would have had if formed by a single lens-a point which, as far as I know, has not been submitted to theoretical investigation). The spurious discs in the reflector being smaller, but the rings more intense, the definition is less pleasant where the rings are conspicuous, as UR enquiries into the nature of telescopic around the larger stars, but sharper where these definition have been restricted to the case appendages are too faint to interfere with the of an uninterrupted pencil of incident rays, when effect, as in viewing the moon, planets, and no other interference takes place excepting that crowded globular clusters (or "resolvable nebula," which invariably arises from its external boundary as they were formerly called). To this we may at the edge of the cell in which the object-glass add, on the score of defect, the feeble interferenceor speculum is placed, or, if the aperture is con- rays proceeding from the arm of the small mirror, tracted, at the edge of the interposed diaphragm; which disturb a little the blackness and neatness but another case requires to be understood, as it of the background of a brilliant star; the irreenters materially into the difference of perfor-gularly refracting currents of air which sometimes mance between achromatics and reflectors. The circulate in the open tube; the increased amount case of an interrupted beam of light, which must of atmospheric imperfection or perturbation inalways occur in reflecting instruments, unless we cluded by the larger aperture; and the necessity adopt the arrangement commonly known as the of occasionally renewing the silver film, and we "front view," or, from its inventor, the Lemairean shall have stated the case fully and fairly against form of telescope. In this the disc and rings the reflector. On the other hand the achromatic should be theoretically the same with those of the has its own special disadvantages-the fringe of refracted image, were it possible to avoid the dis- outstanding colour, or "secondary spectrum," tortion necessarily introduced by the employment around the focal image under high powers, which of oblique reflection; but on account of this is very unpleasant to an eye accustomed to the serious objection, as well as from the irregular picture in the reflector-the unpleasant position of refraction through the heated air, proceeding the head at any considerable altitude, unless a from the observer's head, this mode of mounting diagonal eye-piece is used-and the much greater is not likely to meet with much favour, except for expenditure necessary to secure an equal amount the discovery of feeble nebula or comets, or very of efficiency. minute stars. The success which attended its use The secondary spectrum, just referred to as the in the hands of the two Herschels, at Slough and peculiar drawback of the ordinary achromatic, the Cape of Good Hope, is a striking instance of the may claim a share of our attention. It is the way in which instrumental defects may be counter-necessary result of what is called the "irrationbalanced by experience and skill. But no sooner do we escape the annoyance of a distorted image and a disturbed medium, by the employment of either Gregory's, Cassegrain's, or Newton's construction, than we are confronted by an additional source of interference all round the edge of the small speculum, as well as at each side of the arm which carries it. The latter makes itself sensible in feeble rays, proceeding from the focal image, if of sufficient brilliancy; the former acts in a direction concentric with the interposed body, and of course with the external boundary of the incident light. The effect of this, though more conspicuous than that of the interference of the support of the mirrors, its less injurious than might have been supposed, and in some cases positively advantageous. It is stated by Airy to consist theoretically in a diminution of the spurious disc, with an increase in the number and brightness of the rings, while their diameter is somewhat diminished. Dawes, on the other hand, found practically that the distance of the rings from the disc was increased. I do not know that this discrepancy has been noticed, nor am I able to conjecture its cause; nor do I know what may be the discordant conclusions arrived at by Frauenhofer and Sir J. Herschel, for which Airy

ality," that is, dissimilar ratio or proportion,
of the coloured spaces in the spectra of the two
kinds of glass of which the object glass is com-
posed. Every lens acting as a kind of curved
prism, the image produced by the old refractor,
with a single convex lens as an object-glass, was
full of colour and consequent indistinctness, un-
less the defect were palliated by a most exagger-
ated and inconvenient focal length. In the achro-
matic object-glass (as now made) we have a
convex and concave lens of two kinds of glass,
differing in their power of dispersing white light
and colour, and so adjusted that the colour pro-
duced by the concave corrects or neutralizes that
produced by the convex, while the greater refractive
power given to the convex makes the corrected
rays converge to form a colourless image. If
practice here corresponded with theory, the result
would be, in this respect, perfection. But it so
happens that different kinds of glass not only
differ in their total power of dispersing white into
coloured light, but also in their separate action
on different colours; so that taking the case of
plate and flint glass (which are used for telescopic
work), though we could easily assign such angles
to a prism of each that their spectra would be of
equal length, red ranging alongside of red when

In reflectors there is of course no colour to b corrected; and any defect in this respect must imputed to the eyepiece alone; there is a cre sponding spherical error to be removed, but thes done by the workman in "figuring," as he is a to communicate to the surface that parabic curve which enables it to reflect the central and marginal rays to the same focus; and but fo this controlling power over the figure, the rele tor could never compete, as it may now fairly d with the achromatic. The series of papers Lov drawing to a close has been extended to a very considerable, and some may perhaps think to an undue length. But the subject grew under the hand, outlying materials were gradually ab sorbed into the stream, and points were touchs upon as to which some readers might be fair supposed to need no information. Still, writer hopes his remarks may have been of th others, for whose sake the better instructed bear with his prolixity. It now remains only say what has not been fully said, as to the of a telescope. Much that appertains to t point has already come incidentally before? and we shall scarcely require to be informed in the use of the highest power, the fa image of a bright star by night, or a thermom bulb by day, ought to be a sharp circular d surrounded by a few bright rings, and, as at of the accurate concentration of the rays, it shee be "quick in and out of focus," that is, disti vision should be confined to one position of il eyepiece, and be very rapidly obliterated by r tion either way. There should be no tendency a double image, or radiating flames, or "wings or unsymmetrical distortion of any kind: h patience will often be called into exercise to

Hardwick Vicarage, June 29, 1870.

ELECTRICITY, ITS THEORY, SOURCE,
AND APPLICATION.

The containing vessel is usually a glass bottle, the lower part of which is enlarged with a globe, but this is merely for the convenience of holding a large quantity of solution: any kind or shape of vessel will equally serve. The essential part is the top, to which the plates are secured. This is best made of ebonite, but hard baked wood well soaked with paraffin will answer. In the centre is secured a brass tube, split at the upper part, which projects in order to grip firmly the brass rod which slides in it, and supports the zinc; a plate or wire of metal passes from this tube to the binding screw, which is fixed with the cover for the zinc or connection. This part is often troublesome, as the zinc tarnishes, and imperfect connection follows. The best remedy for this is to thoroughly gild the interior of the tube, and that part of the supporting rod which is in contact with it while the zinc is immersed. It is a great improvement also to form a screw thread on the top of the tube, and fit to it a nut, by tightening which contact is improved, and the zine firmly held up when not in action; also a square tube and rod are better than round ones, as they keep the zinc always parallel with the carbons. The zinc is commonly fixed to the rod by means of a screw on the end, but it is far better to solder them together. I was once greatly troubled with an irregular battery, which I could not keep to its work, though I pulled it to pieces and set everything right, and after great trouble traced the whole fault to this point-acid had found its way into the thread of the screw and entirely destroyed the connection. The carbons are secured to the cover by means of two angle pieces or brackets of brass or iron, as shown (a fig. 42), and these brackets are connected to the cross binding screw. tion is thus one of simple contact, and with a porous carbon it is common for acid to find its way up between the surfaces and destroy the contact. This may be entirely remedied by the plan described in sec. 133, and the upper part of the carbon being coppered the bracket may be soldered to it, and perfect connection ensured, and protected by a covering of paraffin.

criminate between actual defects in je instru- and steady motion is required to keep the object motion of the zinc stirs the liquid up. Thus by ment, and disturbance in the atmos re or tube, in position. In testing an object-glass or setting up the battery in a thin glass vessel to which may produce a marvellous misshapen speculum, such a lens is preferable to a combina- which heat can be applied by a gas burner, I have image, and turn a star into a ball of tangled wool, tion, which may introduce errors of its own; and maintained the current in full even flow until the or, as has been aptly said, "a full blown rose, re- should there appear any defect in the image whole liquid was exhausted. volving upon its axis"! And we must recollect shown in a compound ocular, the removal of the that the moments of best vision are the true field lens answers the same purpose as a change measure of the capability of the instrument. of eye-piece, to show where the fault may lie. A What it has once done, it can always do again. terrestrial eye-piece of four lenses will of course In addition to this focal testing, which we may not be employed, where it can be avoided, render still more severe by unscrewing and laying for astronomical purposes, not only from the loss aside the field-lens of the strongest eyepiece (thus of sight, but from the desirableness of accustommaterially raising the power, though at the ex- ing the eye, as much as possible, to the inverted pense of all but central distinctness), we should image, and reversal of motion through the field, move the eyepiece through a considerable range which characterize the astronomical ocular. on either side of the focus, in order to ascertain And now we shall leave the student with his the regularity of the convergence and divergence instrument, wishing him many a pleasant hour in of the rays. The expanded discs thus viewed the diligent use of it, and above all, that it may should be uniformly luminous (excepting where be the means of aiding him to a more intelligent the "flat in the reflector occasions a central and impressive view of the heavens in their darkness) and accurately circular, bearing in highest and noblest aspect, as showing the handymind, however, that unequally heated currents work of their All-great, All-wise, All-good will sometimes give them an elliptical appearance Creator. T. W. WEBB. in opposite directions on either side of the focus. They ought not in any position to show a much brighter centre, or a ragged outline, and the margin should be as similar as may be on either side of the focus. In a perfect telescope, either achromatic or reflecting, the out-of-focus disc will be bordered by a narrow bright rim within which will BY J. T. SPRAGUE. be a minute black circular line, and within this (Continued from page 341.) again a number of other black hair-lines may be traceable; and if this appearance should be the DELAURIER'S CELL. This is a modification of the bichromate cell lately introduced same on either side of the focus, little more can with a considerable amount of landation; its real be done for the instrument by the skill of man. The test is however a needlessly rigorous one. purpose is simply to obtain a somewhat stronger Great excellence is compatible with a slight dis- solution for the porous cell; because the larger similarity in the interior and exterior discs, aris- cell itself, and plates, with other details of coning from a trifling under or over correction of the struction, are mere matters of arrangement of no spherical error, the former condition being indi- novelty, and equally applicable to other solutions. cated if the border of the disc is sharper within All the remarks made as to the bichromate cell than without the focus, the latter, if the reverse. apply equally to this: its force is the same as "If," says Dawes, "the rings in these out-of-nearly as possible, so also is its rapidly failing focus images are similarly disposed in both cases, current. The added salts add nothing to the the figure is perfect; but a moderate deviation work, they only take oxygen from the bichromate from this perfect equality does not stamp a tele- and reserve it in a more soluble form. I will scope as had, or even unfit for delicate work. therefore only show its cost of working by taking And it is a fact, which I have proved by experi- in grains the quantity given by its introducer and ment, the difference between an object-glass which calulating the cost for pounds as before. The bore this most severe test perfectly well, and one solution is made in the order given, a precipitate which fell obviously short of it, was not to be dis- being at first produced which the acid redisdiscovered by any decided superiority of the one over the other, either in separating power upon close double stars, or even in the perception of faint objects close to bright ones; though this latter is more likely than the former." The same great observer was also of opinion that telescopes under-corrected for spherical aberration usually performed better than those with the opposite, which is also the less common defect. In the same manner we may investigate the true parabolic figure of a speculum.

Each eye-piece ought also to be examined. With the achromatic they will probably be of the Huygenian form, which is excellent, if well constructed, but is too often very carelessly made by rule of thumb." This kind of eye-piece, which is also called "negative," consists of two plano-convex lenses with their convexity towards The object; and if applied simply to the eye as microscopes, they give no image, the focal picture in the telescope falling between the lenses. The eye-pieces of silvered reflectors are either of this form, or more usually Browning's achromatic construction, especially adapted to the instrunent. But occasionally we meet with Ramsden or 'positive' eye-pieces, in which the two enses have each their plane sides outwards, and which act separately as microscopes, the telescopic image falling in the place of an external >bject. These always show colour towards the nargin, an imperfection which the observer must olerate in consideration of the beauty and flatress of the field, rendering it peculiarly suitable or micrometrical purposes. If of any other onstruction, an "ocular" should have a field ree from colour to the edge, as well as equally istinct in every part, without readjusting the cal distance. The Kellner eye-piece, less freuently met with, has a large and beautiful field, at is subject to annoyance from the visibility of agnified dust on the inner surface of the field ns, which is nearly in the focus of the other, nd in the process of frequent cleaning it is liable > be scratched. Single lenses, either plano or ouble convex (Sir W. Herschel, I believe, emloyed the latter), may be very serviceable in exerienced hands, giving a central sharpness not arpassed by any combination; but as the edges f the field are in every respect intolerable, a fine

143.

solves.

300 Water, fluid measure

54 Bichromate of potash at 8d. 432
45 Sulphate of iron
3d. 135
2d. 100

50 Sulphate of soda

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Divided by 7,000 gives 94 Measure sulphuric acid being 3 units, at 0089

⚫0953

·0311

667

•1264

The bichromate here is equal to 1-4 units; but by the time the current had fallen to the same point as with the bichromate cell, page 341, 820 only of useful work was done which brings the cost per unit to 1541 to which adding the zinc as with the other 0293, the total cost is 1834 as against 1406, so that the small advantage gained of the solution lasting a little longer is obtained by increasing the cost nearly one-third.

For use in the single cell the proportions vary somewhat from the above, but the result is the same.

The connec

As the conditions of working of this cell are so variable, it is nearly impossible to make any estimate of its cost. For experiment I fitted up a small cell which, connected with the same coppering arrangement as in other cases, showed at first 65°, falling at five minute intervals to 61°, 53°, 35°. On raising and replacing the plates it rose to 64°, and fell as before; as I did this several times the result would approach to those of ordinary working, and the solution used being equal to 3.54 units, 3-22 of zinc were dissolved, and 1-72 copper deposited. This gives an actual loss by local action of about 87 per cent., and of 100, including the solution left unacted on. The cost per unit being

32.6 zinc, at 7d.
50 bichromate, at 8d.
50 × 2 acid

unit

228

=

400 117, at lid... 146 774

This divided by 7,000, gives per ...1106 which doubled brings the actual cost to 2212, or between a fourth and a fifth of a penny per unit. In order to obtain the greatest economy in working this battery,care should be taken that no larger surface of zinc is immersed than is necessary to do the work. It is the large surface of carbon which most conduces to the effect of the zinc. Only enough is needed to effect the chemical action as fast as it is required; as soon as this is exceeded the local action is favoured, and no advantage gained.

144. BICHROMATE SINGLE CELL.-Though out of the order of classification, it is convenient to deal with this much used cell while on the subject. It consists of two plates of carbon, with one of zinc between them, fitted so that it can be raised out of the liquid. Of late I have noticed in many of the shops small bichromate cells without this fitting, the intention being to let the cells go on working to exhaustion; it is therefore desirable to warn readers against using such cells, which 145.-BICHROMATE SOLUTION.-I must here are most extravagant and unsatisfactory. Used for correct an error made (p. 341) as to the solution the purposes to which it is suited, the bichromate for use with this battery. Describing this in two cell is one of the most useful; it furnishes a most forms (sect. 142), I said the last was similar to powerful current for a very short time, it is there- that usually recommended. The first is really the fore admirably adapted for short experiments with most like the proportion of, acid as 1 to 12, being induction coils, as it gives a greater force than 87 to 1000; the second, 115 to 1000, is of course the nitric acid batteries, and has no unpleasant considerably in excess; observing this I wished fumes, while it can be set aside for weeks and be to examine the calculations afresh and to test reready for action at any instant. But for long-sults. The conclusion I have come to is that the sustained action it is utterly useless, as its force authors who recommend this proportion have confails very fast. The simple action of raising and sidered only the acid required by the salt itself lowering the zinc, however, instantly restores it. and overlooked that needed for the zinc, and that The reason of this is that there is no circulation consequently nearly every one using the bichroin the liquid owing to no gas coming off, and the mate cell wastes unnecessarily one third of the

salt, the most expensive part of the working ingredients. This is evident from the following experiment:-I took 200 grains of solution and

FIG. 42

a

added one twelfth or 17 grains of sulphuric acid and left a piece of zinc in it for 24 hours. The solution is equivalent to 15-39 grains of zinc, but only 11-61 were dissolved. In a similar quantity with 30 grains of acid, the ratio given in the table, 24-82 grains were dissolved. This last is considerably over the equivalent, but the reason is to be found in an action subsequent to the real process-viz., a reduction of the chrome alum by the excess of zinc and the formation of an insoluble deposit; a similar action had occurred in the first solution also, making the apparent action higher than the true one. I may add that the action in the battery of the solution as given by me is much more constant than usual, but the local action somewhat greater both due to increased activity, which produces heat at the surfaces of the plates and a consequent circulation of the fluid, aided by a tendency to giving off a little gas.

It is unnecessary to say anything further of the solution given by Delaurier for the simple cell, as exactly the same remarks apply to it as to that given for use in the porous cell.

146. PERCHLORIDE OF IRON.-This has been recommended for use both in porous cells and in simple cells. I have experimented with it at different times, but with little satisfaction. It has the same disadvantage as the Bichromate rapid failure of current owing to the want of circulation; and therefore I will not occupy space with any particulars, but pass on to those forms of cell in which solid oxidizing agents are employed.

ERRATA.-Page 340, column 3, line 22 from bottom, a full stop instead of comma after "oxygen " breaks the sentence and destroys its meaning; in second line, paragraph 142, "nitrous power" should be "nitrous

fumes."

ECONOMISING HEAT.

length of time), and as a natural sequence, of the
other parts of the vessel. One advantage of this
particular composition is that any person can ap-
ply it; and it lasts a much longer time than the
ordinary felt. A saving of at least 15 per cent.
of fuel is claimed for this composition.

STO

and retains in the shape of vapour charged with tallow. This is true as regards part of the stean. but the other part condenses and falls to the bottom. There is, consequently, a continuou charging of the entering steam with tallow, continuous condensation of entering steam, and e consequent tendency to rise in the level of th tallow floating on the water. To restore th FRICTION IN STEAM CYLINDERS. equilibrium, one of three things may take plas There may be a continuous return flow of vape BY MR. P. JENSEN. ized tallow from or near the surface back into t steam-pipe, and thence into the cylinder, oran (Concluded from page 345.) tinual flow of condensed water, if it could be TORER'S lubricator, patented in 1866, deserves phoned out from the bottom, or a continual fors some notice, because it has been brought a mixture of both. In his latest modificatic prominently before the public. The lid of the Mr. Gamble has contrived a simple mears! lubricator is fixed by means of a bayonet-joint. accomplishing the object, and at the same A screw passes through the lid, and its end is making it a perfect means of regulation. I tightened down on a soft metal seat: this is for steam enters from one side, through a pipe, shutting off the lubricator. A strainer or cage rises into the steam space, part of it falls to a fits over the bottom outlet, which has a cock bottom, as water, while part of it may flow be below for regulating the quantity of steam as greased steam or vaporized tallow. T coming in and grease passing out. Supposing this steam-pipe, at its termination at the centre of the grease cup be filled with suet, which is the apparatus, has a small hole at the tallow level for material it is worked with, the suet will first the entering of the steam, and the egress of the melt, and the light oil which is present in it will greased steam. The steam-pipe has a siph be brought forward and in a profuse quantity pipe screwed into its bottom, reaching nearly enter the cylinder. This is an operation requiring down to the bottom of the lubricator. Into the but very little time; but the suet will remain in inside top of this siphon-pipe a small pipe-th the grease cup for many hours after that, but regulating-pipe-is screwed, which has a s only the gelatinous part of it, which partakes of hole in its side, and has plenty of play round it the nature of glue, and is gradually being distilled when it passes through the steam-pipe. If this off, and is of no use to the cylinder, but rather pipe is screwed down, so as to have the hole in t does it harm. We then see that the action of side at the same height as the steam or tallos this lubricator is very imperfect, very irregular, hole, then, singularly enough, no doubt owing t and, in point of fact, nearly as barbarous as the the capillary attraction, the water will take the old grease cup; nevertheless, it has been brought preference, and will continue to be siphoned out widely into use, and maintains its position on from the bottom as fast as it comes in and con denses, so that little or no lubrication takes account of its cheapness and simplicity. Attwood's tallow-pump, patented in 1864, was place. On the other hand, if the regulating pipe a step in the right direction. Though it has since is screwed up so that its hole comes somewhat been superseded by better means it well deserves over the steam or tallow-hole, then no water will The body of the pump is provided be siphoned out from the bottom, and a very with a steam jacket, to keep the tallow hot, plentiful lubrication with tallow takes place. In otherwise it is fitted like an ordinary pump, with any intermediate position, partly tallow and valves and piston, which latter is worked up and partly water will overflow into the steam-pipe. down by being connected to some reciprocating This can be regulated to the greatest nicety. In part of the engine. The point of attachment is one case, for instance, the engineer in charge made variable to regulate the quantity of tallow said that if the lubricator emptied itself in ten injected. This apparatus ranks intermediately hours it would do. It was set to do it, and did between the old fashioned way of injecting the it. He found that he had more tallow on his whole contents of the grease cup every two hours rods than he wanted. It was regulated accordor so, and the modern way of continuously ingly, and then used its tallow in fifteen hours. greasing the steam. It would even now be useful, He found that he had got more than enough were it not for the often troublesome matter of lubrication even then, and it was accordingly st keeping the valves in proper order, and of arrang- so as to empty itself in twenty-two hours. As ing its connection to the engine, and for the cir- the mill works twenty-two out of the twenty-four cumstance that the engineer in charge is too apt hours, that just suited him. He fills the lubri to forget all about the tallow pump. Finding cator once a day, while oiling round, and does that it gives too much tallow if always at work, not trouble himself further about it, for it wi he throws it out of gear, and often forgets to just use its tallow by the time he has done. throw it into gear till too late. Engineers These lubricators will work in very hot engine in charge of flour-mills, and other works where rooms, without special means for condensing th the power is variable, sometimes say that a steam. The means of regulation are such as La tallow pump is the right thing, or else the old to offer temptation for meddling, for the j grease cup, because the engine often labours screw must be taken out of the top after the key is fitted

[graphic]

a notice.

a

too much, and a sudden injection of tallow is
apparently beneficial, the engine at all events
recovering its speed. A little consideration has,
however, persuaded many of them that this view
of the case is quite wrong; if such a quantity of
tallow is required all at once, and does produce
such a marked effect, what must be the state of
the piston and other internal parts? The
answer is very much too dry. But this would
never happen were the steam properly lubricated.
There is no surer way of clogging the piston-
rings, &c., nor a more likely way of starting red-
lead joints, than by injecting a quantity of tallow
at once. If a mill engine labours occasionally,
the power is not large enough to overcome the
resistance; and it is the wiser plan to improve the
condition of the engine, and thus increase its
actual power, than by dosing it with what might
be likened to a strong dram of neat spirits, all
very well in extreme cases, but very bad taken
habitually.

[OST persons who have any practical aczation of steam are aware of the loss of heat, and consequent waste of fuel and power, caused by the radiation from the unprotected surfaces of boilers and pipes. As the baker wraps his rolls in a blanket, in order to keep them hot for breakfast, so we should cover up our boilers and pipes in some way to prevent the loss of that heat which is in reality the "prime mover. For this reason we wish to call attention to the non-conducting composition of Messrs. Leroy, a circular from whom, with testimonials, is now before us. The advantages claimed for this substance are lightness, cheapness, adhesiveness, durability, and nonconductivity. It adheres to iron and other metals without "lagging" or binding, and while preventing radiation, effectively preserves the iron from rust. It cannot catch fire; and it is not necessary to remove it to examine the boiler, as it shows the smallest leakage immediately. For boilers exposed to the atmosphere, and which are consequently peculiarly liable to injury from unequal expansion and contraction caused by ex- It will have been observed, that all the lubritremes of temperature, it is invaluable, effectu- cators hitherto described are regulated more or ally preventing those evils, as well as securing the less by throttling the steam admission to them, a material from the effects of rust. By applying consequence of which is that the least dirt is apt, this composition to the steam pipes and cylinders, as experience has shown, to stop their action the engine may be removed some distance from altogether. Within the last two years another the boilers without the power of the steam being materially deteriorated.

Applied to the boilers of steam boats it not only economises the fuel, but, by preventing radiation, reduces the temperature of the engine-room (which has hitherto been unbearable for any

lubricator, acting on the displacement principle,
but yet working in a different way to the others,
has been introduced. It is the invention of Mr.
Gamble. The principle of this lubricator is this.
The steam comes in from the steam-pipe, passes
over the surface of the tallow, which it absorbs

into the top of the regulating pipe, and by tam-
ing it a trifle up or down more or less tallow is
fed into the steam. But there is no regulation
by throttling the entering steam by means of the
steam-cock, and neither is there any regulate
by contracting the opening for the overflow of the
tallow. These lubricators are simple in as
struction, and they have no working or wearing
parts that require looking after or setting or re-
newing, and when once regulated they are always
set, no further trouble being incurred than to
draw the condensed water off, and fill afresh with
tallow. As soon as the engine has started its
action begins at once. They are now workin
successfully on marine engines, locomotives,
stationary and portable engines, and are
in suitable sizes for all purposes.

The same principle is carried out in a differe
way by another arrangement. As steam us
sometimes ask for a lubricator with which they
can at any time vary the supply of tallow, the
inventor contrived this arrangement. The authr
contends, however, that this is quite unnecessary
except in very few cases. As before explained. 1
an engine is constantly and properly lubricate
there is practically no need for constant regula
tion of the tallow supply. It is made in th
shape of a hollow plug-cock passing verticar
through the lubricator. The plug has sever!
small ports with corresponding holes in the plas
shell, which is fitted with a siphon-pipe, leadi
to the bottom of the lubricator, the same as the
others. To vary the respective vertical height

of the tallow overflow and water overflow, the plug has a slanting slot corresponding with a horizontal slot in the shell; and by turning the cock to any of the pointer divisions on the outside of the lubricator neck, these levels can be varied

to such an extent as to cause the same action as

above explained with reference to the former class of Gamble's lubricators. The same objection may, however, with justice be urged against this last arrangement as against some of the Inbricators by other inventors, which have been previously described-namely, that any cock arrangement in course of time gets out of order

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Water Analysis: a Practical Treatise on the Examination of Potable Water. By J. ALFRED WANKLYN, M.R.C.S., late Professor of Chemistry in the London Institution, and ERNEST THEOPHRON CHAPMAN. Second Edition, edited by Ernest Theophron Chapman, Member of the Council of the Chemical Society. London: Trübner & Co.

T as, although HIS work, the second edition of which is now analytical chemists, contains but little to interest the general public. The science of water analysis is as yet in its infancy, and while "doctors differ" as to even the method to be pursued in determining the purity of samples of water, it cannot be matter of surprise that we should decline to pin our faith too strictly to one side or the other. This brochure contains elaborate expositions of the experiments of Messrs. Wanklyn and Chapman to arrive at the relative salubrity of the waters supplied to some of our most important towns; and while agreeing in the main with the conclusions of these gentlemen, we cannot but acknowledge that there is room for some more definite settlement of the vexed question of the impurity of water and the method of its analysis. The new matter in this edition consists of a chapter on the Tetration of Waters, a Modification of the Process for the Estimation of Nitrates, and a Method of Estimating Minute Traces of Lead; chapters on the Volatile Organic Matter present in Water, and on the Purification of Water. But there is no information which will serve to guide the public in the choice of a filter, though a few remarks of interest to our readers are contained in the following paragraph.

"Slow filtration through a layer 4in. thick of animal charcoal in coarse powder removes all organic matter from water, or almost all; but the charcoal fouls to some extent, and after it has been in use with a bad water for some length of time it lets much of the organic matter pass. If we take some of this charcoal out, and treat it with permanganate of potash and potash, we shall get off ammonia from it in large quantities, proving the presence of organic matter; but if we let it stand for some hours in the air, nearly all the organic matter will be oxidized and disappear."

After all that has been said as to the impurity of the water supplied to the metropolis, it is some consolation to be told that average London water from the Thames contains only 0-03 per cent. of impurity. We are at present very much in the dark with regard to the sanitary aspect of the amount of solids existing in water. Whether a water having an exceptionally small amount of solid contents is specially salubrious remains to be ascertained. A very large quantity of fixed matter is certainly unwholesome; for instance, sea-water is absolutely non-potable. But whether the twenty-one grains per gallon present in London water, or even double that amount, would do the smallest damage to the health of any one who should drink it, is an open question.

Undoubtedly sewage-contaminated water is and must be unwholesome, and it is matter for regret that nearly all the water supplied to London has been tainted at one time or another; but whether

it is completely purified by contact with the hundreds of the surrounding population-were I, oxygen of the air or is delivered in its impurity, perhaps, the heir or the head of an aristocratic is still a question for the savants, and the sooner name, and influenced by the feelings I now possess it is settled the better for the credit of our -then some good might arise from the advocacy of scientific men, if not for the health of the people. the claims of such as would work if work there were to do. It cannot be denied but that in this enlightened country the vast majority of questions goodness or badness of the questions themselves.

Transactions of the Woolhope Naturalist's Field

Club, 1869. Hereford.

There is

NATURAL history societies and naturalists' field clubs are doing good work through the length and breadth of the United Kingdom. scarcely a county which does not possess its coterie of "lovers of nature" and amateur philosophers, and by their untiring efforts (though here and there strongly tinged with egotism) we are rapidly acquiring a complete knowledge of the whole country. The club whose transactions the flora and fauna, the bryology and fungology of are now before us most certainly ranks as one of the best, as this volume of its proceedings amply testifies. In the record of what was done in 1869 by the members of the Woolhope Naturalists' Field Club we find papers on a variety of interesting subjects, some of course more particularly concerning the county of Hereford, others of interest to the whole kingdom. Thus, for instance, a paper on Spheroidal Structure in Silurian Rocks; Meteorology, by Balfour Stewart; Richardson's Forces of Electrical Discharge; some excellent illustrations, with descriptions, of the edible fungi of Herefordshire; and last, but certainly not least, a Claris Agaricinorum, by Mr. Worthington G. Smith, now first published, together with a complete list of the British Agarics. The president, in the address with which he closed his year of office, speaking on the subject of mushrooms, said:"Edible funguses, by their chemical constituents, are known to be highly nutriof animal food; but hitherto the ignorance of those forms which were wholesome has deterred most people from making any use of them beyond the common mushroom. Without this practical knowledge it is undeniable that serious mistakes may be made, and therefore, the great aim of our fungologists should be to lay down some easily comprehended rules for the diagnosis of wholesome species." This the Woolhope Club are doing admirably, by giving coloured illustrations and minute descriptions of every variety found in the county of Hereford. Those illustrated in the present volume bear the inviting names of "Vegetable beefsteak," Vegetable sweetbread," and "Plum mushroom." There is also a drawing of the "Hedgehog mushroom," which the Rev. W. Houghton describes as "one of the most excellent fungi that grows its flavour very strongly resembles oysters." Besides the lithographs of the fungi there are photographs of two celebrated oaktrees in the county of Hereford, and to Mr. Worthington Smith's valuable "Key of the British Agarics," there are some plates of typical forms of fungi coloured to match the natural tints of their species; indeed, in the matter of illustration no expense seems to have been spared to render Transactions of the Woolhope Naturalists' Field Club" what it really is, a valuable book.

the 16

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EMIGRATION.

A FEW REMARKS ON VICTORIA.-(Concluded.) BY "F.R.G.S." MANUFACTURES.

IT is with mingled feelings of regret and pleasure flourishing colony. that I pen these last remarks upon this In the attempt to convey information-whether that attempt be good or badI always derive pleasure, but I sincerely regret the circumstances which call for any such information as that contained in my humble efforts. It is a momentous question to be decided, which places home, friends, and fatherland, combined with want associations, with plenty of work on the other. I feel there rests a great responsibility upon every writer on this subject. Many people are tempted to make a decision to emigrate here or there, as the case may be, by the advocacy of popular writers or demagogues paid by interested persons to whitewash every drawback-nay, more, to paint every. thing in the most gorgeous colours that can be imagined. How careful then should every conscientious person be who dabbles with this question. How deliberately should his statements be chosen, his extracts weighed; for if one person is finds the fact stated therein fallacious, ruin is the influenced by one sentence, and upon experience result, but the responsibility rests upon the writer's shoulders. Could I, by high flights of oratory and rhetoric, pour forth the despairing accents of

of work, on the one hand, and a new country, new

are settled by influence, and not from the innate

Millions are spent annually upon a vast army and navy, upon material for destroying our fellow men; but where do we find brotherly love, the hand of fellowship, or the suffering of an imaginary (or real) wrong, without persistent efforts at retaliation. But what has this to do with emigration? I say, much. Look at New Zealand. Ten centuries hence the acts of Englishmen will be read with abhorrence. Go to Australia. Have the Aborigines force appropriate their property, and laugh at their suffered nothing at our hands? Do not we perfutile efforts to recover it, paying the price of our shores were to go with a Christian determination to inheritance by extermination? If the thousands who now annually leave our do what is right, we should soon hear no more of these terribly merciless massacres which every now and then flash meteor-like from America, Australia, or New Zealand.

Having given vent to various pent-up feelings, and mentioned subjects requiring long and calm meditation, I return to my subject. The manufactures of Victoria were for many years scarcely worth mentioning, and even now it is difficult to say what is the staple manufacture of the colony.. Perhaps that which has latterly drawn most attention is the preservation, &c., of meat. Owing to the scarcity of animal food in England, ingenious minds turned their attention to the importation of "meat" from the countries where superabundant South America and Australia "animals" existed.

Far

were looked upon as the great "flesh-forming emporiums." Companies were floated for the purpose of these is the "Melbourne Meat Preserving Company." At a recent meeting a dividend of 10 per cent. was declared, and a balance of more than £9,000 was carried over to the reserve fund. more important to my readers than the percentage gained is the statement of payments for labour. I find that for a longer period than the past eight months the company has paid away weekly a sum of not less than £1,000 for labour and materials. In six months 160,752 sheep and 590 oxen had been disposed of, and there was every prospect of more extended and more successful operations. Better than dwelling upon the various manufactures, I will give a list of the raw materials of the colony, taken from an elaborate prize essay by C. Mayes, C.E., entitled "Essay on the Manufactures more immediately required for the Economical Develop ment of the Resources of the Colony":

MINERAL SUBSTANCES.

coal, feldspar, gems (diamonds, topaz, beryl, &c., Basalt, clay (pottery and fire), cement, stones, &c.), gold, iron (hæmatite, &c.), limestone, man-ganese (oxide), quartz, salt, tin, &c.

VEGETABLE SUBSTANCES.

Arrowroot, almonds, bark, barley, beet-root, beans, carraway, cucumber, castor-oil plant, colza-oil plant, cabbage, fruits (mostly similar to English), gum (various), grapes, grape seed, hemp, hop, lavender, maize, mulberry, narcissus, olive, oat, orange, poppy, potato, rose, sassafras, tobacco, wheat, walnut, &c., &c.

ANIMAL PRODUCTS.

Offal (all kinds-e.g., bones, furs, horns, hoofs, &c., &c.), kides, &c., tallow, and wool.

Most of these products are utilized to a greater or less extent, and therefore readers will be able to form an opinion regarding the manufactures :ADDENDA II. (From the Times, June 28.)

Commerce was held in Melbourne on the 20th April. The annual general meeting of the Chamber of The retiring president, Mr. Lorimer, read his annual address, and in reviewing our recent commercial history he touched on many topics interesting to commercial men in all parts of the world. After remark

ing on the depressed state of trade during the past year, which he attributes to excessive importations, he

proceeds as follows:

furnished by the Customs' returns, does not exhibit any great increase in the importations of last year, when considered in connection with the increase of population. The total value of imports in 1869 was

"A reference to the statistics of our import trade, as

£13,908,990, including £1,415,473 for gold, the produce of New Zealand. It was pointed out last year that this gold was included in the returns of imports for the first time in 1868, and it is therefore necessary to deduct the item from the returns of both years in order to institute a fair comparison with previous ones. We then get a value of £12,493,517 for all other imports in 1869, as against £12,014,836 in 1868. The population during the year increased from 683,977 to 710,284, so that the value per head of the population 1869. rose from £17 11s. 4d. in 1868 to 217 11s. 9d. in This increase may to some appear unimportant, but it must be borne in mind that for our importations have been our actual wants, and that the changes in the circumstances of the people have considerably

years

in excess

of

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