212 ANNUAL OF SCIENTIFIC DISCOVERY. 



surface. When these various products come in contact with the pre- 

 pared cotton, the latter is moistened by the vapor of water, and the 

 tannin retains the nicotine in chemical combination. The distin- 

 guished chemist, Cahours, has repeated Terrier's experiment, and 

 confirmed his results. He is convinced that by the use of the cot- 

 ton prepared by M. Ferrier, and removed sufficiently often, thejpro- 

 ducts of the combustion and distillation of tobacco are entirely 

 deprived of nicotine. Barral, without disputing the result of Fcr- 

 rier's experiments, objects that nicotine is not capable of uniting with 

 tannin, and that the latter substance is not less injurious than nico- 

 tine. The conclusion to be derived from these investigations seems 

 to be, that tobacco-smoke which has passed over prepared cotton is 

 not absolutely deprived of its virtue. Besides, it yet remains to be 

 ascertained whether smoke thus deprived of its nicotine would still 

 have the properties required by the smoker. Says Barreswill, it 

 would seem that if tobacco were employed only for its smoke, and 

 not for the physiological effects which the smoke produces, it would 

 be easy to substitute for it some inoffensive substance, or even to 

 abstain entirely from its use, unless, indeed, the mere mechanical 

 operation of breathing gas through the tube of a pipe, or cigar, is not 

 all the pleasure of smoking, or the odor of tobacco, aside from its 

 special influence, does not have a sufficient attraction. It is not diffi- 

 cult to conceive that persons may become habituated to the use of 

 tobacco thus deprived of its peculiar qualities, when we remember 

 that chicory has become a regular article of consumption, being used 

 to make a coffee which may be truly considered as destitute of all 

 virtue. 



CURIOUS FACTS IN RELATION TO PICRIC ACID. 



Mr. M. Carey Lea, of Philadelphia, states that the characteristic 

 yellow color of picric acid is so powerful that he has found that water 

 is distinctly colored by one-millionth of its weight of the acid. This 

 color is also totally destroyed by sulphuric acid of a certain strength, 

 without in any way decomposing the acid. 



Water containing one ten-thousandth of picric acid exhibits a 

 bright yellow color. With one three-hundred-thousandth the color 

 is still distinct, even in a stratum of not over an inch in thickness. 

 But in large quantities a millionth gives a distinct color, as above 

 mentioned. 



THE EQUIVALENT OF HEAT. 



The mechanical equivalent of heat has been determined by M. 

 Jule, of Manchester. He found that one unit of heat, or that quan- 

 tity of heat which is necessary for raising the temperature of a 

 pound of water one degree centigrade, is equivalent to the mechani- 

 cal work by which the same mass of water is raised to 423^ metres, 

 or 1389 English feet. When heat produces mechanical power, that 

 is, mechanical work, a certain amount of heat is always lost. On the 

 other hand, heat can be also produced by mechanical power, namely, 

 by friction and the concussion of unelastic bodies. You can bring a 

 piece of iron into a high temperature, so that it becomes luminous 



