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THE following is the farewell address of Dr. Liwson, lato Editor of Scientific Opinion: — •' Varions correspondents have kindly expressed their regret that the present Editor shonld cease to hold the reins of Scientific Opinion. We thank them for their good feeling. Much of the success which has attended our labours has been tine to the gênerons help and friendly advice, ftiggestion, and encouragement held ont by our correspondents, and especially by one who, we do not hesitate to say, is the first man of Science of the age. Bnt, in retiring from the Editorial chair, wo do so not without a feeling of relief, even if tinged with regret at losing pleasant intercourse with many respeoted colleagues. The task of conducting a weekly journal, which shall not, as certain journals are, be as it were, pitchfoTked together, and of so considering tlíe current of politico-scientific questions as to be enabled to help pnblic opinion on its way to reform, is so arduous, so unceasing, attended with so much anxiety, and such intense unrest, that after nearly two years of editorial toil, we lay down опт bnrden and are glad to be able to put in practice the old aphorism, ' Rest and be thankful.' We believe that onr successor will not lose sight of the interests of those who have во long and so favourably supported Scientific Opinion, and in resigning to him the Editorial chair, we bid a kind adieu to our old friends, and ■wish our future representative Ood-speed in all heartiness and goodwill."
WORKING MEN'S EXHIBITIONS.
AFTER nearly twenty years of experience it has been discovered that in order practically to interest working men in artistic and industrial exhibibitions, they must be partakers in their management, and share the rewards of success. At the Agricultural Hall, Islington, there is to be a display, commenced during the present month, in which this principle will be, for the first time, amply recognized. Celebrated firms and large employers of labour will compete; but to every specimen of ambitious handicraft will be affixed the name of the artisan who wrought it, so that, by obtaining a prize, he will carry a perpetual certificate of skill, which can scarcely fail him, even in the worst of times. A few attempts of a similar kind have been made in England, but upon a limited scale, and under mistaken arrangements. At the Floral Hall, for instance, and at the Mechanics' Institute, in Leeds, working-class emulations have been seen; yet they bore an amateur and immaturo appearance. We regretted to find so much ingenuity anrt patience wasted upon elaborate patchwork qnilts representing every colour in the uniforms of the British army, tables and tea-caddies, combining a thousand pieces of wood ; antomaton chimes, and other monuments of devotion, illustrating a Chinese dexterity and perseverance, b.-.t not improving either the position or the capacity of the worker. At present we have no means of judging how far this or a different system has prevailed at the Agricultural Hall, but there is reason to believe that the emulation »ill be seriously and strictly industrial. It is to ge international, яя we have said. Now a great «ifficnlty has always stood in the way of communication between the artisans of one country i'i.1 those of another. The cost of travel is one obstacle. The want of a common langnage is anchor. The value of time, to people who, by daily fiort, earn their daily bread, is a third. Still, as tor superior working-classes will find, in course of
time, when more habituated to these rivalries, they are of immense, and even immediate use. We are kept out of many fields by that rarest of all senti ments—a national modesty. This point requires explanation, which we hasten to give. It is a popular idea, among us, that we can never hope to vie with the weaver of Lyons in the production of silk tissue. Why not? Lyons borrowed her cunning from Venice, buys a principal part of her machinery in Great Britain, and imports her raw material, as we do, from China, Persia, and Italy. At Paris, at Amsterdam, at Munich, at Wittenberg, at Leipsic, at Mayeuce, last year, specimens from the English loom were shown which by no eye could have been distinguished from the finest of French manufacturers. So, too, with porcelain, with bronze, with all the fictile arts. We have been deafened out of self-respect by foreign praises of foreign wares, and have been in danger of forgetting that which in reality we ourselves have taught to half the world. Not, by any means, that we would counsel conceit or complacency on the part of our workmen when exhibiting; but a due consciousness of merit is a Bpccies of wholesome pride. Next week, no doubt, when the French and Italian artisans are among us, we shall recognize, in both, the signs of a peculiar genius, worth stndying, and deserving to be applauded. But, to get a true gain from a movement which, unquestionably, will grow into a European custom, we must trace for it the right direction, and point for it a practical end. In enforcement of this view we would indicate some specialities of International Exhibitions in the post. To begin with, they have not generally afforded fair play to tho artisan; they have been too much dedicated to arte, to luxury, to fancy, fashion and the voluptuousness of civilization. Then, flourishing and renowned houses, winning diplomas, gold medals, honorary mentions, and other awards, have completely drained out of sight the merit of the individual workman. What did we hear of him, the associate-artist of all the strong and beautiful elaboration, in 1851, in 1855, in 1862, in 1867, and in other years when the earth was supposed to be, in lauréat language, "blessed with all the fruits of peace, and crowned with all her flowers." This time, however, his toil, invention, and mastery over his craft, will be patent, and, while the employer will enjoy the credit of knowing a good workman, tho workman can claim the credit of his own performance. This is as it should be. We shall witness greater results from a series of Working Class Exhibitions than even working men themselves are prepared for—all to their advantage, all to their elevation in the social scale. Let us refer to one episode. In 1868, the peat-cutters of the Belgian frontier—an entirely rural population— and the skilled mechanics of the Amsterdam building-yards—men utterly distinct in habits, culture, and modes of thought, conceived together the idea of an International Exhibition on the banks of the Amstel. They wanted the one from the other to learn new lessons in industry and life; and, while excluding no class, they resolved that the Exhibition in the Dutch capital shonld principally represent their own. Their attention was given to houses and their materials, plans of dwelling-rooms, bed-rooms, kitchens, and yards; samples of mortar, cement, concrete, ironwork, and means of рисventing damp, and foundations. They next considered cheap and useful furniture, and found that the world had a larger plenty for their comfort than they had imagined—seaweed for softening theirbeds, compressed tan to make warmth for their wintere, and an infinitude of trifles, adding much, however, to the cheap facilities of their domesticity. So with clothing, they multiplied its economies for themselves. So with food. They detected eatable qualities in a thousand things hitherto despised. So, once more, with tools. They compared their own with the implements of other nations, and even learnt leseons from the flint axe of a thousand years ogo. The art of life on the Continent is never lost sight of in working men's exhibitions. Nevertheless, it is perhaps true that their main and ultimate object mnst be the advance of the workman in his craft, and his power of triumphantly competing not only with his fellows from the Continent, bnt also with tho necessities of his age. Much has been said and written of late concerning the importance of technical education. Mr. Samnelson, of Banbury, compiled for Parliament a very important Blue Book ou this subject. In it he endeavoured to show that the British artisan was inferior in many respects to tho French, the Belgian, and the
German ; the Russian, Spanish and Italian being hon de ennceurs. Now there was a good deal of plausibility in all this. Workmen's mechanical schools, no doubt, abound more on the mainland of Europe than in these islands; but we are not aware of any failure which has been humiliating to the working class genius of England in the international competitions which have taken place. Indeed, it strikes us that this is not the real question involved. It is not whether we are outdone by rivals; but whether we might not outdo ourselves as we are, by what we are capable of being. To that result do these workmen's exhibitions tend, and in that prospect we must welcome them. The choral workman's song, sung in Dutch at Amsterdam, sets forth the idea, and, if a free translation may be pardoned, we quote from it one stanza :—
Ko monster of iron, or gunpowder-fed,
Ко cblngour of steel, no whizzing of lead,
Makett the blood in oar urteries tingle;
But the whirl of the wheel, and the whistle of steam,
And the bubbling kins of the seething stream,
Is the sound where our sympathies mingle.
Of course a Workmen's Exhibition may be intended to serve one of two purposes, or the two together. It may be designed to meet the many wants of his class which have hitherto been unprovided, or it may aim at extending his power over the materials which he has to manipulate, so that his ability shall exceed that of his rivals belonging to other nations. Or, we repeat, it may attempt both purposes. We are inclined to think that the former scheme is the more important. Taking the two, however, together we may assign them to seven descriptions. The first is that of habitations. When the poor, herded in crowds, occupy common lodgings, mingling their wants and miseries, losing all sense of individuality and home, they become inevitably demoralized, and no work so good has been done on the Continent as that which has been done in connection with exhibitions, by teaching the industrious classes that their dwellings may bo cheap and yet decent, humble and yet very comfortable. The Belgians and the Prussians are far in advance of all other nations in this respect, although the Dutch may claim a high preeminence on account of their model workshops. As to furniture, it may confidently be said that our working classes do not understand it at all. A Dutch or a German cottage inhabited by a family, the united earnings of which do not average 20s. a week, will exhibit a neatness, a snngness, and a completeness which we should look for in vain, as a rule, in the homes of our artisans. We should like to find some of our working class exhibitors turning their attention to the means of economising space, and securing ventilation in their abodes. In Northern Europe, in Sweden and Denmark, for instance no such evil as that of foul air is ever heard of. Again the idle time of continental workmen, apart from the Parisian, is rarely really idle. It is devoted to invention, to gardening, or to simple contrivances for the house, and that is a reason why so many more comforts are found in the Dutch or German cottage than in the English. In the matter of clothing, a great advantage possessed by the foreign artisan is that, having the raw material so much at his own door, his family have not yet given np the practice of manufacturing for him and themselves; but no donbt that is an exceptional circumstance of which we shall hear very little when capital and machinery have completed their conquests. The distaff is doomed at the first glance of the loom. It is, indeed—passing from the domestic necessities suggested by the varieties of а Working Men's Exhibition—the future control nud improvement of the new forces constituting the industrial power of modern nations that is the chief object of emulation. It is the implement for fieldwork, for the workshop, for the factory, that is to bo perfected; and if in our day an artisan discovers how to multiply and bring into more direct action these forces, he may win not only a medal or a mention, bnt a chance of fortune in its most worldly sense. We have witnessed of late years many proofs of this from among the dykebuilders of Holland, the most self-contained country in the world, China excepted; and its agriculturists and its net-makers have arisen rich firms which command the markets of Europe. The leather-dealere of Mayence, many of them not long ago only journeymen, have so profited by their skill that they have no competitors in Germany, and even supply our Australasian colonies. The opticians of Leipsic hold their ground against oil comers. The Venetian glass manufacturer has his home in London—and not
one of these industries exists which has not been promoted by the emulous spirit of international exhibitions. We would therefore counsel our mechanics to take these opportunities in Rood earnest, and to appreciate the chances they offer of general and personal advantage. The world knows too little of its workmen. Thousands of tasks finished by apt and patient hands, tender suggestions of form and colour, marks of thoughtful capacity aud memorials of loving care, like that bestowed by Ascanio on his lily, abound in the workshops whence, hitherto, no name has ever issued forth to fame. It is with pleasure then, we notice that in the forthcoming exhibition which Her Majesty has privately visited, and the Prince of Wales will open, the personal merits of the workman will be recognized. Indubitably while he demonstrates his own high quality he will perceive that he has much to learn from his fellows, and we trust, notwithstanding our denial of the idea that foreign workmen are, upon the whole, inferior to ours, ho may yet be so unprejudiced as to acknowledge that something may be taught to him by the Frenchman, the Dutchman, or the German. How is it that we cannot make articles de Paris! How is it that we are ntterly beaten in toy-making by the manufactories of Nuremburg? This localization of peculiar industries is among the most unintelligible of phenomena. A workmen's exhibition brings it however before the workman's eye, and sets him reflecting npon his position in the great race of industrial nations. At an exhibition he can see clearly on what courses, and for what prizes, he is first,second,or third,or not placed at all. We have every confidence in the prowess of our exhibitors at the Agricultural Hall, but would prefer that our mechanic should look to the exhibition less for triumph than for teaching.
HINTS TO ASTRONOMICAL STUDENTS.
OUR enquiries into the nature of telescopic
refers to the articlo on " light " in the " Encyclo-
But at any rate the general result is, that the
This then is one great difference between the definition of equally perfeot 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 around the larger stars, but sharper where these appendages are too faint to interfere with the effect, as in viewing the moon, planets, and crowded globular clusters (or "resolvable nebulie," as they were formerly called). To this we may add, on the score of defect, the feeble interferencerays proceeding from the arm of the small mirror, which disturb a little the blackness and neatness of the background of a brilliant star; the irregularly refracting currents of air which sometimes circulate in the open tube; the increased amount of atmospheric imperfection or perturbation included by the larger aperture; and the necessity of occasionally renewing the silver film, and we shall have stated the case fully and fairly against the reflector. On the other hand the achromatic has its own special disadvantages—the fringe of outstanding colour, or "secondary spectrum," around the focal image under high powers, which is very unpleasant to an eye accustomed to the picture in the reflector—the unpleasant position of the head at any considerable altitude, unless а diagonal eye-piece is used—and the much greater expenditure necessary to secure an equal amount of efficiency.
The secondary spectrum, just referred to as the peculiar drawback of the ordinary achromatic, may claim a share of our attention. It is the necessary result of what is called the "irrationality," 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 composed. Every lens acting as a kind of curved prism, the inmge produced by the old refractor, with a single convex lens as an object-glass, was full of colour and consequent indistinctness, unless the defect were palliated bj a most exaggerated and inconvenient focal length. In the achromatic 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 produced by the concave corrects or neutralizes that produced by the convex, while the greater refractive power given to the convex makes tho corrected rays converge to form a colourless image. If practice here corresponded with theory, the result would be, in this respect, perfection. Bnt 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 ot each that their spectra would be of
violet matched violet, we should find still that green
In reflectors there is of course no colour to rx? corrected; and any defect in this respect must be imputed to the eyepiece alone; there is a corresimuding spherical error to be removed, but this is done by the workman in " figuring," as he is able to communicate te the surface that parabolic curve which enables it to reflect the central and marginal гаув to the same focus ; and but for this controlling power over the figure, the reflector could never compete, as it may now fairly do, with the achromatic. The scries of papers now drawing to a close has been extended to a very considerable, aud some may perhaps think to an undue length. But the subject grew under tho hand, outlying materials were gradually absorbed into the stream, and points were touched upon as to which some readers might be fairly supposed to need no information. Still, the writer hopes his remarks may have been of use to others, for whose sake the better instructed will bear with his prolixity. It now remains only to say what has not been fully said, as to the trial of a telescope. Much that appertains to this point has already come incidentally before us; and we Bhall scarcely require to be informed that in the use of the highest power, the focal image of a bright star by night, or a thermometer bulb by day, ought to be a sharp circular disc surrounded by a few bright rings, and, as a t«et of the accurate concentration of the rays, it should be "quick in and out of focus," that is, distinct vision should be confined to one position of the eyepiece, and be very rapidly obliterated by motion either wuy. There should be no tendency to a double image, or radiating flames, or " wiuRS," or unsymnietrical distortion of any kind: hot
equal length, red rauging alongside of red when | patience will often be called into exercise to
criminate between actual defects in ijie instrument, and disturbance in the atinosj'^re or tube, which may i>roduce a marvullouiii/ misshapen image, and turn a star into a ball oí tangled wool, or, as has been aptly said, " a full blown rose, revolving upon its axis "! And we must recollect that the moments of best vision are the trne measure of the capability of the instrument. What it has once done, it can always do again. In addition to tills focal testing, which we may render still more severe by unscrewing and laying aside the field-lens of the strongest eyepiece (thus materially raising the power, though at the expense of all but central distinctness), we should move the eyepiece through a considerable range on either side of the focus, in order to ascertain the regularity of the convergence and divergence of the rays. The expanded discs thus viewed should be uniformly luminous (excepting where the "flat" in the reflector occasions a central darkness) and accurately circular, bearing in mind, however, that unequally heated currents will sometimes give them an elliptical appearance 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 Le a minute black circular line, and within this again a number of other black hair-lines may bo traceable ; and if this appearance should be the ваше on either side of the focus, little more can be done for the instrument by the skill of man. The test is however a needlessly rigorous one. Great excellence is compatible with a slight dissimilarity in the interior and exterior discs, arising from a trifling under or over correction of the spherical error, the former condition being indicated if the border of the disc is sharper within than without the focus, the latter, if the reverse. "If," says Dawes, "the rings in these out-offocus images are similarly disposed in both cases, the figure is perfect; but a moderate deviation from this perfect equality does not stamp a telescope as had, or even nuiit for delicate work. And it is a fact, which I have proved by experiment, the difference between an object-glass which bore this most severe test perfectly well, and one which fell obviously short of it, was not to be disdiscovered 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 вате 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 eyo 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 moro usually Browning's achromatic construction, especially adapted to the instrument. But occasionally we meet with Ramsden or "positive" eye-pieces, in which the two lenses have each their plane sidee outwards, and which act separately as microscopes, the telescopic image falling in the plaee of an external object. These always show colour towards the margin, au imperfection which the observer must tolerate in consideration of the beauty and flatness of the field, rendering it peculiarly suitable for inicrometrical purposes. If of any other construction, an "ocular" should have a field Bree from colour to the edge, as well as equally distinct in every part, without readjusting the focal distance. The Kellner eye-piece, less freflncntly met with, has a large and beautiful field, put is subject to annoyance from the visibility of bagnifiod dust on the inner surface of the field leus, which is nearly in the focus of the other, tod in the process of frequent cleaning it is liable Ь be scratched. Single lenses, either piano or loeble convex (Sir W. Herschel, I believe, emJoyed the latter), may be very serviceable in ex•rienced hands, giving a ceutral sharpness not Jrpasecd by any combination; but as the edges tí the field are in every respect intolerable, a fine
and steady motion is required to keep the object in position. In testing an object-glass or speculum, such a lens is preferable to a combination, which may introduce errors of its own; and should there appear any defect in the image shown in a compound ocular, the removal of the field lens answers the same purpose as a change of eye-piece, to show where the fault may lie. A terrestrial eye-piece of four lenses will of course not be employed, where it can be avoided, for astronomical purposes, not only from the loss of sight, but from the desirableness of accustoming the eye, as much as possible, to the inverted image, and reversal of motion through the field, which characterize the astronomical ocular.
And now we shall leave the student with his instrument, wishing him many a pleasant hour in the diligent use of it, and above all, that it may be the means of aiding him to a more intelligent and impressive view of the heavens in thenhighest and noblest aspect, as showing the bandywork of their All-great, All-wise, All-good Creator. T. W. Wedb.
Hardwick Vicarage, June 29, 1870.
ELECTBICITY, ITS THEORY, SOURCE,
Вт. J. T. SriiAouE.
(Continued from page 341.)
ШОвиагав'вCell. Thisisa modification . of the bichromate cell lately introduced with a considerable amount of laudation; its real purpose is simply to obtain a somewhat stronger solntion for the porous cell ; because the larger cell itself, and plates, with other details of construction, are mere matters of arrangement of no novelty, and equally applicable to other solutions. All the remarks made as to the bichromate cell apply equally to this: its force is the same as nearly as possible, so also is its rapidly failing current. The added salts add nothing to the work, they only take oxygen from the bichromate and reserve it in a more soluble form. I will therefore only show its coet of working by taking in grains the quantity given by its introducer and calnlating the cost for pounds as before. The solution is made in the order given, a precipitate being at first produced which the acid rediseolves.
300 Water, fluid measure
50 Sulphate of soda „2d. 100
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 wasdone 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, bnt the result is the same.
144. Bicheomate Single Cell.—Though out of the order of classification, it is convenient to deal with this much used cell while ou 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 are most extravagant and unsatisfactory. Used for the purposes to which it is suited, the bichromate cell is one of the most useful; it furnishes a most powerful ourrent for a very short time, it is therefore admirably adapted for short experiments with induction coils, as it gives a greater force than the nitric acid batteries, and has no unpleasant fumes, while it can be set aside for weeks and be ready for action at any instant. But for longsustained uction it is utterly useless, as its force fails very fast. The simple action of raising and lowering the zinc, however, inetantly restores it. The reason of this is that there is no circulation in the liquid owing to no gas coming off, and the
motion of the zinc stirs the liquid up. Thus by Betting up the battery in a thin glass vessel to which heat can be applied by a gas burner, I have maintained the current in full even flow until the whole liquid waB exhausted.
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 solntion: 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, spUt at the upper part, which projects in order to grip firmly the brass rod which elides 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 beet 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 zinc 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 whol e 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 tig. 42), and these brackets are connected to the cross binding screw. The connection is thus one of simple contact, and with a porous curbon 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 paralfin.
As the condition к 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, 8-22 of zino 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 zino, at 7d 228
50 bichromate, at 8d 400
50 x 2i acid = 117, at lid... 146
This divided by 7,000, gives per
which doubled brings the actual cost to 2212, or between a fourth and a fifth of a penny per unit. In ordor 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.
145.—BicHnoMATE Solution.—I must here correct an error made (p. 341) as to the solution for use with this battery. Describing this in two forms (sect. 142), I said the la.il was similar to that usually recommended. The first is really the most like the proportion of, acid as 1 to 12, being 87 to 1000; the second, 115 to 1000, is of course considerably in excess; observing this I wished to examine the calculations afresh and to test results. The conclusion I have come to is that the authors who recommend this proportion have considered only the acid required by the salt itself and overlooked that needed for the zinc, and that consequently nearly overy one using the bichromate cell wastes unnecessarily one third of the
added one twelfth or 17 grains of sulphuric acid and left a piece of zinc in it for 34 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 procees—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 oft' a little gas.
It is unnecessary to say anything further of the solution given by Delaurierfor the simple cell, as exactly the same remarks apply to it as to that given for use in the porous cell.
146. Pebchloridk Op Ikon.—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.
Rruata.—Pasto 340, column 3, line 22 from bottom, a full »top instead of comma after " oxygen " break» tbe sentence and destroys its meaning; in second line, paragraph 142, "nitrooa power" should be *' nitrous fumes."
MOST persons who have any practical acquaintance with the production and utilization of steam are aware of the loss of heat, and consequent waste of fuel and power, cansed 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 reafitythe "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, oheapness, adhesiveness, durability, and nonconductivity. It adheres to iren 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 extremes of temperature, it is invaluable, effectually preventing those evils, as well as securing the material from the effects of rust. By applying this composition to the steam pipes and cylinders, the engine may be removed some distance from the boilers without the power of the eteam 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
length of time), and as a natural sequence, of tho other parts of the vessel. One advantage of this particular composition is that any person can apply 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.
FRICTION IN STEAM CYLINDERS.
Bï Mb. P. Jensen.
(Concluded from paye 345.)
STOKER'S lubricator, patented in 1800, deserves some notice, because it has been brought prominently before the public. The lid of the lubricator is fixed by means of a bayonet-joint. A screw passes through the lid, and its end is tightened down on a soft metal seat: this is for shutting off the lubricator. A strainer or cage fits over the bottom outlet, which has a cock below for regulating the quantity of steam coming in and grease passing out. Supposing this grease cup be filled with suet, which is the material it is worked with, the suet will first molt, and the light oil which is present in it will be brought forward and in a profuse quantity enter the cylinder. This is an operation requiring but very little time; but the suet will remain in the grease cup for many hours after that, but only the gelatinous part of it, which partakes of the nature of glue, and is gradually being distilled off, and is of no use to the cylinder, but rather does it harm. We then see that the action of this lubricator is very imperfect, very irregular, and, in point of fact, nearly as barbarous as the old grease cup; nevertheless, it has been brought widely into use, and maintains its position on account of its cheapness and simplicity.
Attwood's tallow-pnmp, patented in 1864, was a step in the right direction. Though it has since been superseded by better means it well deserves a notice. The body of the pump is provided with a steam jacket, to keep the tallow hot, otherwise it is fitted like an ordinary pump, with valves and piston, which latter is worked up and down by being connected to some reciprocating part of the engine. The point of attachment is made variable to regulate the quantity of tallow injected. This apparatus ranks intermediately between the old fashioned way of injecting the whole contents of the grease cup every two hours or so, and the modern way of continuously greasing the steam. It would even now be useful, were it not for the often troublesome matter of keeping the valves in proper order, and of arranging its connection to the engine, and for the circumstance that the engineer in charge is too apt to forget all about the tallow pump. Finding that it gives too much tallow if ulways at work, he throws it out of gear, and often forgets to throw it into gear till too late. Engineers in charge of flour-niills, and other works where the power is variable, sometimes say that a tallow pump is the right thing, or else the old grease cup, because the engine often labours hard when the stones are pressed together a little too much, and a sndden 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 tho 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 pistonrings, A.c., nor a more likely way of starting redlead 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 tho 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.
It will have been observed, that all the lubricators hitherto described are regulated more or less by throttling the steam admission to them, а consequence of which is that tho least dirt is apt, as experience has shown, to stop their action altogether. Within the last two years another 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 comos in from the »team-pipe, passes over the surface of the tallow, which it absorba
and retains in the shape of vapour charged with tallow. This is true as regards part of the steam, but the other part condenses and falls to the bottom. There is, consequently, a continuous charging of the entering steam with tallow, s continuous condensation of entering steam, and a consequent tendency to rise in the level of the tallow floating on the water. To restore the equilibrium, one of three things may take place. There may be a continuous return flow of vaporized tallow from or near the. surface back into the steain-pipe, and thence into the cylinder, ora continual flow of condensed water, if it could be н phoned out from the bottom, or a continual flow.if a mixture of both. In bis latest modification. Mr. Gamble has contrived a simple means of accomplishing the object, and at the same tâc making it a perfect means of regulation. Trw steam enters from one side, through a pipe, ind rises into the steam space, part of it falls to the bottom, as water, while part of it may flow back as greased steam or vaporized tallow. Tin? steam-pipe, at its termination at the centre of the apparatus, has a small hole at the tallow level for the entering of the steam, and the egress of the greased steam. The steam-pipe has a siphonpipe screwed into its bottom, reaching nearly down to the bottom of the lubricator. Into the inside top of this siphon-pipe a small pipe—the regulating-pipe—is screwed, which has a small hole in its side, and has plenty of play round it when it passes through the steam-pipe. If this pipe is screwed down, so as to have the hole in it3 side at the same height as the steam or tallowhole, then, singularly enough, no doubt owing to the capillary attraction, the water will take the preference, and will continue to be siphoned out from the bottom as fast as it comes in and condenses, so that little or no lubrication taktä place. On the other hand, if the regnlating pipe is screwed up so that its hole comes somewhat over the steam or tallow-hole, then no water will be siphoned out from the bottom, and a rery pleutiful lubrication with tallow takes place. In any intermediate position, partly tallow find partly water will overflow into the steam-pipe. This can be regulated to the greatest nicety. In one case, for instance, the engineer in charge said that if the lubricator emptied itself in ten hours it would do. It was set to do it, and did it. He found that he had more tallow on his rods than he wanted. It was regulated accordingly, and then used its tallow in fifteen hours. He found that he had got more than enough lubrication even then, and it was accordingly set so as to empty itself in twenty-two hours. As the mill works twenty-two out of the twenty-four hours, that just suited him. He fills the lubricator once a day, while oiling round, and does not trouble himself further about it, for it will just use its tallow by the time he has doue. These lubricators will work in very hot enginerooms, without special means for condensing Um steam. The means of regulation are such as not to offer temptation for meddling, for the jam screw must oe taken out of the top after the steam has been shut off. A little crutch key is fitted into the top of the regulating pipe, and by turning it a trifle up or down more or less tallow is fed into the steam. But there is no regulation by throttling tbe entering steam by means of tho steam-cock, and neither is there any regulation by contracting the opening for the overflow of the tallow. These lubricators are simple in construction, and they have no working or wear-in*; parts that require looking after or setting or re newing, and when once regulated they arc 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 workim: successfully on marine engines, locomotives, stationary and portable engines, and are made in suitable sizes for аБ purposes.
The same principle is carried out in a different way by another arrangement. As steam users sometimes ask for a lubricator with which they can at any time vary tho supply of taJlow, the inventor contrived this arrangement. Tho atith-r contends, however, that this is qnite unneccBsary. except in vary few cases. As before explained, if an engine is constantly and properly luhricat«d, there is practically no need for constant re^c-alstion of the tallow supply. It is made in ttu shape of a hollow plug-cock passing vertioalli through the lubricator. The plug has so*c«?raJ small ports with corresponding holes in the p'n£ shell, which is fitted with a siphon-pipe, 1я*<1ш; to tbe bottom of the lubricator, the same as th others. To vary Ute respective vertical heii*ir.i of the tallow overflow and water overflow, the plug has a slanting slot corresponding with » horizontal slot in the shell; end 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 ишв 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 lubricators by other inventors, which have been previously described—namely, that any cock arrangement in cours« of time gets out of order by eonstaut wear.
'The author has now, it is hoped, shown that Htenm lubrication is a subject well worth taking into account in steam-engine economy; also, that the continuous system is the only correct one, and ought to be more generally introduced, wherever the old-fashioned and wasteful intermittent system ha» been found better than no lubrication at all. It is therefore important that engineers should more generally take notice of these facts, which form a small link in the large chain of steam economy.
it is completely purified by contact with the oxygen of the air or is delivered in its impurity, is still a question for the "rants, and the sooner it is settled the better for the credit of our scientific men, if not for the health of the people.
Water Analyri»: a Practical Treatise on the Examination of Potable Water. By J. Alfred Wanxlxx, M.B.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.
THIS work, the second edition of which is now before us, although doubtless invaluable to 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 honrs 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 а 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
Transactions of the Woolhope Naturalists Field Club, 1869." Hereford. Natural history societies and naturalists' field clubs are doing good work through the length and breadth of the United Kingdom. There is 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 flora and fauna, the bryology and fungology of the whole country. The club whose transactions 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 mush rooms, said :—" Edible funguses, by their chemi cal constituents, are known to be highly uutri tious, and in B great degree supply the elements of 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 the " Transactions of the Woolhope Naturalists' Field Club " what it really is, the valuable book.
A Few Remarks On Victoria.—(Concluded.)
IT is with mingled feelings of regret and pleasure that I peu these last remarks upon this flourishing colony. In the attempt to convey information—whether that attempt be good or bad— I always derive pleasure, but I sincerely regret the circumstances which call for any such information as that contained Hi my humble efforts. It is a momentous question to be decided, which places home, friends, and fatherland, combined with want of work, on the one hand, and a new country, new 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 everything in the most gorgeous colours that con 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 influenced by one sentence, and upon experience finds the fact stated therein fallacious, ruin is the 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
hundreds of the surrounding population—were I, perhaps, the heir or the head of an aristocratic name, and influenced by the feelings I now possess —then some good might arise from the advocacy of 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 are settled by influence, and not from the innate goodness or badness of the questions themselves.
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 suffered nothing at our hands? Do not we perforce appropriate their property, and laugh at their futile efforts to recover it, paying the price of our inheritance by extermination '.'
If the thousands who now annually leave our shores were to go with a Christian determination to 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 tosay what is the staple manufacture of the colony. Perhaps that which has latterly drawn most attention is the preservation, ice, 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 "animals" existed. South America and Anstrahlt were looked upon as the great "flesh-forming emporiums." Companies were floated for the purpose of preparing the "meat," and the most successful of these is the "Melbourne Meat Preserving Company." At a recent meeting a dividend of 10 per cent, was declare.1, and a balance of more than £9,000 was carried over to the reserve fund. Far 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 ram materials of the colony, taken from an elaborate prize essay by C. Majes, CE., entitled "Essay on the Manufactures more immediately required for the Economical Development of the Resources of the Colony " :—
Mineral Substances. Basalt, clay (pottery and fire), cement, stones, coal, feldspar, gems (diamonds, topaz, beryl, Ate., ifcc), gold, iron (hreinatite, <tc), limestone, manganese (oxide), quartz, salt, tin, &c.
Vegetable Substances. Arrowroot, almonds, bark, barley, beet-root, beans, corraway, 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, &e.
Offal (all kinds—e.g., bones, furs, horns, hoofs, &c, .vim. Lides, &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, Jane 28.) The annual general meeting of the Chamber of Commerce was held in Melbourne on the 20th April. The retiring president, Mr. Loriincr, read his annual address, and in review hie our recent commercial history he touched on many topics interesting to commercial men iu all parts of the world. After remark big on, the depressed state of trade during the past year, which he attributes to excessive importations, he proceeds as follows '.—
"A reference to the statistics of our import trade, as furnished by the Customs' returns, does not exhibit any great increase iu the importations of last year, when considered in connection with the increase ot population. The total value of imports in I860 was £18,908,990, 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 1808, 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 £12,498,517 for all other imports in 1809, as against £12,014,838 in 18C8. The population during the year increased from 689,977 to 719,284, so that the value per head of the population rose from £17 lis. 4d. in 1868 to £17 lis. ¡M. in 1869. This increase may to some appear unimportant, but it must be borne in mind that for years our importations have been in, excess of our actual wants, and that the changes in the circumstances of the people have considerably