Oct. G, 1882. 



♦ KNOV/LEDG2 



315 



the silver solution. Being then engaged in electro-depositing as a 

 business, and these iniprovemeuts economising the process con- 

 siiicrably, I kept them secret for awhile, and sold my phosphorus 

 solution at a good profit, as bisulphide of carbon then cost 2s. per 

 ounce retail, and witli one ounce I could make above twenty ounces 

 of the "improved" solution by merely adding the cheap oil and 

 turpentine. I sent a considerable quantity to St. Petersburg. 



Practically, however, the method is of very little value. The 

 crab, buttertly, and beetle .shown by Prof. Christian may be better 

 preserved by simple drying ; and the brain of a rabbit, or other 

 soft putrescent object,' only show all their details, as described, 

 when the film of metal is too thin to preserve the object in its 

 original form. If made thicker, it becomes rough and warty, as 

 all wlio are practically versed in electro depositing well know, and 

 the object is thus defaced. 



But for this, works of art in plaster of Paris might be converted 

 into bronzes by simply coating them with copper. I worked at this 

 for some time and made such bronzes, but they were very unsatis- 

 factory. The artistic finish of the original was marred by the 

 coating of metal, just as such things are too often spoiled by 

 successive coats of paint. 



The prettiest application is for the silvering or gilding of skeleton 

 leaves, or similar light objects requiring only an immeasurably thin 

 film of metal. This has survived, and is, I believe, still practised. 



There is another and far more practical use of the silver pre- 

 cipitation of phosphorus — viz., that of forming a conducting 

 surface on wax moulds and other matrices.- I used it largely in 

 conjunction with plumbago, depositing the silver first, and then 

 brushing over with the plumbago. Sly solution was thus used in 

 St. Petersburg, and may now be useful to some of the readers of 

 Knowledge. W. Mattieu Williams. 



DEFECTS OF BICYCLES. 



[587] — AH riders capable of forming a judgment, and free Jrom 

 prejudice, will agree with your excellent correspondent, Caleb 

 Adams, in the opinion he expresses respecting the defects of the 

 modern bicycle, but what makes his letter of such especial value at 

 the present time is that a determined effort is now being made to 

 import the defects of the modern bicycle into the tricycle. A 

 number of gentlemen, principally racing bicycli^ts, have been 

 endeavouring for months past to introduce path racing for the tri- 

 cycle, alleging, as the principal value of such races, the great im- 

 provement that will result from proper machines for racing pur- 

 poses being built by the manufacturers, and thus great alterations 

 being made in the tricycles which have to be ridden on the road. 

 Doubtless the result of this would be much smaller springs, with 

 less elasticity, and, to reduce weight, mnch smaller steering-wheels. 

 Such alterations would produce little effect that could be felt cither 

 on the asphalte track or cinder path, but would be destructive of the 

 good qualities of the tricycle for riding over ordinary roads or 

 touring purposes. John Browxixg. 



[588]— I should like to add a few words to the letter of Mr. Caleb 

 Adams (No. 531, page 235). With the general tenor of his ex- 

 jicrience ray own experiments agree, but surely Mr. Adams has 

 overlooked the efforts of the best modern makers to supply a spring 

 which shall be at once neat and efficacious. The " Arab " and 

 Uillman's " gig" spring will readily occur to the practised rider as 

 samples of what I mean. 



The small back wheel adds greatly to the appearance of the 

 machine, and its ill effects may be almost entirely counteracted by 

 using a large-size rubber tyre on it. So far as the comfort of the 

 rider goes, the thicker tyre should be on the back wheel, instead of 

 on the front. 



As to large saddles, this is entirely within the personal control of 

 ever}- rider. Lamplugh, the great saddle maker, supplies all sizes, 

 from immense tricycle saddles, suitable for sixtecn-stone riders, to 

 the smallest racing saddle, and any size is readily affixed to any 

 bicycle. I have this season used a very largo size with the best 

 results. U. T. llou.VD. 



Letters in Type. — Physiological Exreriment, by 7,. ; Talking 

 Canary, ic, by Charles L. Cane; Dr. Hunter's Experiments, by 

 Mathilde Van Evs ; Coincidences, by A. U. W. ; Lapidaries and 

 Deception, by IL M. W.; Figure Training by Corsets, by Alfred 

 Chadwick, M.D ; The Fifteen Puzzle, by A. B. ; Flint Jack, by 

 E. T. r. W. ; Long Tricvcle Hide, by J. F. P.; Spiritualism, by 

 E. P. W. 



SixPExcE each will be paid for copies of Nos. 2 and 5 of Know- 

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mmunicationt for tht Editor requiring early attention should reach the 

 ■ be/ore the Saturday preceding the current w*«« of KkowledgB, the 

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HiKTS TO CoBBBSPOSOBSTS.— 1. Xo queitiont atking Jor tcintific ii/ormation 

 can be antvered through the poet. 2 Ltttere tent to the Editor for corretpondeute 

 cannot befortcardtd, nor can the namee or addrenet of correipondentf be gicen in 

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ekould be made to it* number, the page on which i 



J. H. W. L. Fancy many would not like portraits. It sti-uck me 

 at the British Association that the insides of scientific heads are, as 

 a rule, better than the outsides.— T. H. Thanks. That subject 

 (the seas) is full of interest. Have dealt with it in the first paper 

 of my " Poetry of Astronomy," " When the Seas were Young," but 

 will try to find room for a paper on the subject in Knowledge 

 soon. — Jas. Pearson- : Will notice it soon. — W. C. Thomas, T. H., 

 P. BoswoKTH Smith, D. R. C. J. Caswell, A. J., H. J. Watson, 

 J. W. Williams, E. H. Leexey, J. H. W. L., Eben. Jokes, wish 

 the weather chart discontinued. — Ex. Wv., Lionel T. Wal- 

 ler, J. EorxDHEAD, 51. Meees, and others, would prefer some 

 weekly weather record, but are content, if the majority are, 

 that KxowLEnGE should be without it. — Ax Old SrBscRiBEB tells 

 us that a highly scientific friend approved highly of the Charts — 

 Jonx Gkeenfield thinks that as we still recognise the mark of 

 Balaam's rod on the ass's back, and the impression of Peter's 

 thumb on the haddock (also on the John Dory), so may we find in 

 the earth's tilt a mark of " its having been moved to prevent the 

 snn's setting when Joshua wanted more light to defeat the 

 Amalekites." Science raises its hat to Mr. Greenfield, and bowing, 

 passes on.— C. J. Caswell. I liked the tables myself ; but they 

 were denounced lustily. Fear your friend will hardly enjoy the 

 joke so much as you do. — D. R. Effects of interference too 

 complex, I fear, for discussion here. But two persons not near 

 each other, and both at a considerable relative distance from an 

 orchestra, should hear similar sounds, just as two ships tolerably 

 far from the region where various causes have troubled a sea, are 

 similarly affected, though not near each other. At any given moment, 

 the undulatory conditions are, of course, unlike; but the general 

 effect is the same. — Rendrag. Will find space for the balloon extract 

 if possible. — G. S. Silent lightning is common when the air is 

 moist ; it indicates less electric tension than is present in ordinary 

 thunderstorms. You say it seems to leap from the" ground ; and in 

 books we often sec the" statement that lightning is generally seen 

 to pass from the clouds to the earth, though occasionally the 

 other way. But it is demonstrable that no eye can tell which way 

 the lightning travels. — D. Davie,<. An obvious misprint — probably 

 tables stereotyped. Do not know the ballad about half-crown 

 and run-over boy. — H. A. Bvlley. It seems to me, as a layman, 

 that there is much truth in yonr remarks ; but I fear readers of 

 Knowledge would object to a discussion in these columns of the 

 relative merits of homa'o|)athy and allopathy.^ — E. D. Wareixc. (1) 

 What do you understand by salt water? If yon mean simply a 

 solution of common salt in water, the easiest way of distinguishing 

 salt water from sea water would be by tasting. But if you wish to 

 know how sea water may be distinguished from other kinds of salt 

 water, the answer would depend on their nature. In ordinary 

 sea water common salt forms only about two-thirds of the solid 

 matter, of the rest the chief constituents are chloride of mag- 

 nesium and sulphate of soda (about 5i parts and -ii parts, 

 respectively, in a thousand). Carbonate of lime and silica 

 are also present. (2) I do not know how sulphate of iron 

 stains can be removed from white marble. Perhn]>s some reader 

 can inform us. — E. Brvxetti. I fear it is hopeless to try to move 

 the M.C.C. to any change.— F. C. S. Your letter about smoking 

 and growth is, unfortunately, too long. I think it is only smoking 

 by young lads which is supposed to interfere with growth. But, 

 for "my own part, I look with great distrust on statistics of that 

 sort. On the other subject (alcohol and brainwork), space is a 

 little overcrowded just now. I want that list of letters in type to 

 be shortened quickly.— M. G. Olpham. The difficulty is that it is 

 Edward, not Henry, "in Lm Monties, the Abbe's own iwpor. A " slip 

 of the pen " woui'd hardly account for such a mistake. Many 

 thanks for your kindly expression of opinion about Knowledge. — 

 E. R. More astronomy now, since some readers arc so prt?Fsing. 

 1 was so bashful, you i.erceive.-J. H. W. L. Fonr. without the 

 specimens our zoological and geological contributors ci'uld hardly 

 decide. The geological question would be especially difficult. Of 

 course, the dental formula, in the other case, is not right for the 

 dog, the likeliest animal otherwise. Are you sure about the molars ? 

 — iGNORAMfs No. II. (1) Do "objects at a distance look smaller 

 than they really are t " If your question means why do objects look 



