By the chemical analysis of hair it is found to consist of nine different substances: 1st, gelatine or animal matter, which constitutes its greater part; 2d, a white concrete oil in small quantity; 3d, another oil of a grayish-green color more abundant, these oils comprising about one-fourth of the entire weight; 4th, a few particles of oxide of manganese; 5th, iron, the state of which in the hair is unknown; 6th, phosphate of lime; 7th, carbonate of lime in very small quantity; 8th, silex in greater abundance; 9th, and lastly, a considerable amount of sulphur--such is the constitution of all furs, wools, hair, &c., most of which may be dissolved in pure water heated to a temperature above 230° of Fahrenheit, by which it is partially decomposed. Hair is likewise soluble in alkalies, with which it forms soap. Chlorine gas immediately decomposes it, producing a viscid mass. It is worthy of particular remark, that of all animal products, hair is the one least liable to spontaneous change, evidence of which may be found in the fact that the Peruvian, Mexican, and Brazilian mummy hair is still perfect, and is supposed to be from 2500 to 3000 years old, and stands the hygrometric test with equal firmness. From this we should suppose the body or substance of hair and wool to be exceedingly hard and solid, which is really the case, as no pressure has yet been applied sufficiently powerful to entirely deprive wool of the water with which it has been washed--the interstices between the fibres of the assemblage never having been closed by the power applied, as the water therein collected may still be drained off when the pressure is removed. Although hair is of a tubular construction, yet all varieties are not of a completely cylindrical form; a curl is the result of all flat-sided or oval hairs, the exceeding oval being the unfailing characteristic of the negro race. A cross section of a hair, if circular, denotes the long, soft, and lank fibre of a cold northern animal; but if the cross section shows an extreme flat-sided hair, that hair will be crisp and frizzled, and of a tropical extraction. Quite a gradual change in the form of the fibre of hair is observed in all animals as we ascend from the equator to the highest latitudes, other things being equal. It has long been a desideratum how to discriminate between the various qualities of hatters' _fine_ furs, and no really reliable test has yet been obtained, superior to the judgment of the human eye, the fineness of fibre for the hatter being of most essential importance, particularly that allotted for the flowing nap upon the outside of the hat. Although the thickness of the fibre of the finer furs has never been properly gauged, it will be a source of some satisfaction to know that the diameter of the human hair varies from the 250th to the 600th part of an inch, while the fibre of the coarsest wool is about the 500th and the finest about the 1500th part of an inch.