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Mi ne r al s sent for examination should be distinctly mark ed or labeled. (6677) W. H. B. says: What preparation ie best for tanning cat and other small hides with the fur on, so that the skin will be soft and yet strong ? A. Supposing the skins are dry, they shonld be softened throughout by soaking in pnre water; soft water is best, bnt any ordinarily pure water may be used, and care must be taken that the skins are thus soaked only a sufficient time to soften them. Then clean off any bits of flesh that may remain on the flesh side, rinse all well, shake off the loose water, and gently stretch out and tack on a board, flesh side up. Then sprinkle with a mixture of powdered alnm and salt, abont twothirds alum and one-third salt, enough to just COver every part. As tbe skin dries it takes np the mixture, but if any be left on the surface the second day, sprinkle on a little more wa ter, otherwise pnt on more alnm and salt, and sprinkle. Two to three days shonld be sufficient for such small skins, the ideE heing to give the skin all the alnm and salt it wil! take up, while in a moist condition. This tawing process makes the hair firm, a gentle rubbing and beating softens the flesh side, and it is preserved from decay, although tawed skins are never calculated to stand much wetting. This process is well adapted for all small skins, althongh those which are heavier require mOle time, and the flesh sides are sometimes folded together, and the skins rolled up. When tbe skins are freshly taken off, no soaking is needed, but more care is the.n callen for in thoroughly washing off and cleaning them, and the first application of salt and alum should be in the proportions of onehalf each. It requires the judgment of a tanner to deal with skins in a dry state which may have become partly damaged before drying, and it requires special knowledge also to tell whether a dry skin is so damaged. (6678) P. W. J. says : Can you give me some information regarding the nature of alloys ? A. The following is from Hiom's "Mixed Metals": " When two or more metals are caused permanently to unite, the resulting mixture is termed an alloy. When mercury is an essential constituent, the mixture is termed an amal. gam. The general method of effecting combination is by the agency of heat, but with certain soft metals trlle alloys may be formed by subjecting the constituents to considerable pressure, even at the ordinary temperature. Alloys such as those briefly referred to were doubtless first discovered by the metallurgical treatment of mixed ores, from the simnltaneous reduction of which alloys would be formed; or in some cases, as in ores of gold aud silver, naturally formed alloY5 would be obtained by a simple melting proce,s. The direct preparation of alloys by the simple melting together of the constituent metals has been enormously developed in modern times, and the attention which mixed metals are now receiving by chemists is far greater than in any period of bistory. Cumparatively few of the metals possess properties such a. render them suitahle to be employed alone by the manufacturer; but most of tbem have important applica. tions in the form of alloys. Even among the metals which can be used independenly, it is often found expe. dient. to add portions of other metals, to improve or oth erwise modify their pbysical properties. Thus gold is hardened, and made to resist wear and tear, as well as to lower its cost, by the addition of copper; silver is like wise hardened by alloying it with copper; and the bronze coinage is formed of an alloy of copper, zinc and tin for SImilar reasons." (6679) E. W. B. says: Can you tell me how to preserve bird skins ? A. Make an incision from 397 the breast bone to the vent; with a small piece of wood work the skm from the flesh. When the leg 18 reached, cut through the knee Jomt and clear the shank as far as possible, then wind a bit of cotton wool on which some arsenical soap has been put round the bone; do the same With the other leg. Now dlVlde spine from root of tail, takmg care not to cut too near the tail feathers. or they will come out. Next skm the wings as far as possible and cut off The skin will now be entirely clear of the body. The skin must now be turned inside out and the neck and skin gently pulled in opposite directions till the eyeballs are fully exposed The "holc of the back of the head may be cut off and the eyes and brams taken out and thetr places filled with cotton wool. The whole skin should be rubbed "ell with arsenical soap or plain arse' nic, and the neck returned to its natural positIOn, when, after filling the body "ith a little dry grass or wool, the Job is done. It is very easy, and the skin of a bird is much tougher than one would suppose, though. of conrse. they vary, the night-jar being very thin, while hummmg birds are , fairly tough. All the apparatus required is a sharp knife and a pair of scissors, Of, for large birds. a strong pair of nippers to diVide the Jones. ( For further mformation see works on taxidermy. (6680) P. W. P. says: Will you kindly give me directions for the amalgamatIOn of zincs ? A. ThiS IS accomphshed in several ways. 1. By dipping the zinc in dilute sulphuric aCid and then dippmg the end of it into a .maH quantity of mercury, after rubbing the surface with a brush. 2. Dissolve I lb. of mercury in 5 II). of mtromuriatic aCId (mtric acid 1 part. muriatic acid 3 parts). heat the solution gently to hasten the action. When a complete solution of the mercury IS effected, add 5lb more of nitromuriatic acid. The solutIOn should be aj plied with a brnsh, as immersing the zinc in it is wastefnl. 3. 'fo the bichromate solntion commonly nsed in batteries, addl to every pmt of solution 1 drachm of bl' sulphate of mercury or a similar amonnt of nitrate of mercnry (mercury dissolved m Oltric acid). By employ. mg thIS method, the amalgamation of the zincs IS maintained continuously after the first amalgamation, which must be accompil"hed by method I or 2. (6681) A. F. R. says : Can you give me directions for indexing ? A. A writer says: Having had to index twenty nine thonsand words, I think I have a right to speak about it. In the first place I got hold of a somewhat stimsh paper (old ledger paper is excellent); then I cut it into silps of different size (one inch by two inches Will be about right). I put down on each slip a word or sentence (depending on the kind of index), with page and other reference if such is necessary. When every word or sentence which I wanted in the index was noted down, I got hold of twenty-six Cigar boxes. which I lettered from a to z. I now distributed those slips into the boxes. 'fhis done. I pnt the contents of each box in a separate paper bag, put the now empty boxes again before me, got hold of a and dlstnbuted all .lips bear ing words beginnmg "ith a between these boxes. thns, aa, ab, ac. ad. etc. to the end of the chapter. This done, I got hold of aa and successively ab, ac, etc. and dis tributed those slips further. When arranged alphabetically, I pasted those slips belonging to a in proper order on brown wrapping paper. Having treated a in this "ay. I took hold of b, and so on to the end of the alphahet. It took me a fortnight (six hours a day) to get through with the dIStribution. and after that the copying took me several months.