25. _Flexible Ivory._--M. Charriere, a manufacturer of surgical instruments in Paris, has for some time been in the habit of rendering flexible the ivory which he uses in making tubes, probes, and other instruments. He avails himself of a fact which has long been known, that when bones are subjected to the action of hydrochloric acid, the phosphate of lime, which forms one of their component parts, is extracted, and thus bones retain their original form and acquire great flexibility. M. Charriere, after giving to the pieces of ivory the required form and polish, steeps them in acid alone, or in acid partially diluted with water, and they thus become supple, flexible, elastic, and of a slightly yellowish colour. In the course of drying, the ivory becomes hard and inflexible again, but its flexibility can be at once restored by wetting it either by surrounding it with a piece of wet linen, or by placing sponge in the cavities of the pieces. Some pieces of ivory have been kept in a flexible state in the acidulated water for a week, and they were neither changed, nor injured, nor too much softened, nor had they acquired any taste or disagreeable smell. 26. _Air-Whistle._--Mr C. Daboll, of New London, Connecticut, has invented a whistle that speaks with a most "miraculous organ" whenever its services are required for the purpose of alarm or warning. It is designed for the use of vessels at sea or on the coast, as on our eastern shores, where dense fogs prevail, and vessels are liable to come in collision before they are conscious of each other's approach. Its great advantage is its power of communicating sounds for a distance of from 4 to 5 miles, far exceeding the largest bells. An experimental one has been placed on Bartlett's Reef, and the pilot of the "Lawrence" states that he has heard it when about 4 miles off from Bartlett's Reef, _against the wind_, which was blowing quite fresh at the time. This was on a clear day, and when the whistle was blown at his request, and also by advice of the inventor, so that the distance might be marked. It is probable that, under the same circumstances, the tones of a bell could not have been heard more than from one half to three-fourths of a mile. The pilot of the steamer "Knickerbocker" reports, that he _made the whistle_ during a dense fog, thirteen minutes' running-time of the steamer, before coming up with the station where it is located. He therefore must have been some four or five miles distant from it when he heard it.