Page:Popular Science Monthly Volume 32.djvu/734

714 soap resin is added. Soft soap is prepared from fatty substances, with potash. Cocoanut-oil soap has the advantage of being usable with sea-water, and is often called marine soap. Carbolic-acid soap contains about two per cent of carbolic acid, and has antiseptic as well as washing properties. In toilet soaps, as in old brown Windsor, when they are kept for a long time, the soda is influenced by the air and has its strong properties neutralized. Then it is remelted and stored up again, and remelted a second time, when it becomes soft and tender; but the toilet soaps of the present are not always given time to age. Pears's soap is ordinary soap of good quality, cut into shavings, dried, and treated with alcohol. The alcohol evaporates and leaves the transparent soap. The treatment has the effect of taking all the free soda out of the mixture.

Genesis of "Original" Rocks.—Dr. T. Sterry Hunt gave, in the British Association, a concise account of his theory of the genesis of the various groups of original or non-clastic rocks, which he classifies on the basis of their geognostic relations as indigenous, exogenous, and exotic masses. The superficial portion of a cooling globe, consolidating from the center from a condition of igneous fusion, he conceived to have been the protoplasmic mineral matter, which, as transformed by the agencies of air, water, and internal heat, presented a history of mineralogical evolution as regular, as constant, and as definite in its results as that seen in the organic kingdoms. The author next considered the conditions of softening and displacement of indigenous rocks, which permitted them to assume in many cases the relations of exotic rocks, and to become extended after the manner of lavas, as seen in the case of trachytes and many granite-like rocks. Such masses he designated pseudo-plutonic.

Efficiency of Explosives.—It is pointed out by Professor Charles E. Munroe, in his "Notes on the Literature of Explosives," that the theoretical efficiency of an explosive "can not be realized in useful work for several reasons, viz.: because of incomplete explosion; because of the compression and chemical changes induced in the surrounding mineral; because of the energy expended in cracking and heating rock which is not displaced; and because of the escape of considerable quantities of the gases through the blast-hole and the fissures made by the explosion. In all probability the extent of these losses can never be determined by direct experiment, as the phenomenon of an explosion does not admit of a close observation; nor can it be determined by comparison with the work done under other circumstances, as we are as yet uncertain as to the so-called dynamic resistance of rock. The useful work of a blasting charge is employed partly in shattering the rock and partly in throwing or displacing the shattered masses. It is a familiar engineering problem to reduce the projectile force of a blast to a minimum by means of suitable sized charges, properly located in blast-holes of estimated dimensions, and so avoid the cannonading of which workmen are fond. With the discovery of at least approximately correct values for the useful work of charges, we are now able to demonstrate the correctness of this principle."

Mistakes in treating Organic Refuse.—Most of the shortcomings of modern sanitary methods, says Dr. G. V. Poore, are due to the fact that, in our dealing with organic refuse, we commit a scientific error—i.e., we pursue a course that is in opposition to natural law. This error consists in mixing organic refuse with water. It then undergoes changes which differ widely from the changes which it undergoes when mixed with earth. According to Wollny, the process of oxidation of organic matter and the formation of nitrates take place most readily when a moderate amount of moisture is present, and the most favorable amount is about thirty-three per cent. When water is in excess, the amount of free oxygen is insufficient to favor the growth of mold-fungi, the schizomycetes (bacteria and micrococci) are formed, and, in place of oxidation, putrefaction occurs, with the formation of ammonia, free nitrogen, carbonic acid, and carbureted hydrogen. This process of deoxidation takes place in mixtures of putrescible matter with water, and takes place also, it is said, in soil which is thoroughly soaked in sewage. In