682 THE POPULAR SCIENCE MONTHLY. 



can divorce themselves from it without losing their capacity. As 

 a whole, tobacco is harmless to the mind, but it may have a mis- 

 chievous influence on the health, and may cause serious diseases. 

 We should not advise any one to use it, and should try to keep 

 women and children from doing so. In taking up this part of its 

 programme, and in affiliating itself with teachers of all grades, 

 the Society against the Abuse of Tobacco has performed real serv- 

 ice ; but it has tried to gain its end by exaggerations that can 

 only compromise it. It is of no use, and would be labor lost, to 

 try to convert adult smokers so long as they experience no incon- 

 venience from the habit. As soon as they begin to feel some 

 troubles, and have reached an age when the troubles may become 

 grave, the dangers to which they are exposing themselves should 

 be described to them without extenuating them, but without mak- 

 ing the picture blacker. If dangerous affections are threatened, 

 like angina pectoris, or injuries to the tongue and lips, a decisive 

 course must be taken, and the immediate and complete abandon- 

 ment of the cigarette and pipe insisted upon, for experience has 

 taught that there can be no gradual leaving off. Translated for 

 The Popular Science Monthly from the Revue des Deux Mondes. 



ODORS AND THE SENSE OF SMELL. 



By M. CHAKLES HENRY. 



A CONSIDERABLE number of mineral compounds are odor- 

 ous. It is enough to mention, as illustrations of the fact, 

 the sulphureted hydrogen odor of rotten eggs, and the scent of hy- 

 drocyanic acid which emanates from bitter almonds. Although 

 perfumes, or pleasant smells, are organic or carbon compounds, 

 the distinction between organic and inorganic may be considered 

 artificial, since the principal organic bodies can be obtained by the 

 combination of such simple mineral elements as carbon, oxygen, 

 hydrogen, and nitrogen. On the gradual complication of synthe- 

 ses of this kind M. Berthelot, who has made more of them than 

 any other chemist, has based a classification of organic compounds 

 into eight categories. We have first, hydrocarbons, formed of the 

 two elements acetylene, formene, benzene, turpentine, styrolene, 

 etc. The bodies composed of three elements carbon, hydrogen, 

 and oxygen are divided among four categories. We distinguish 

 between the alcohols, which are capable of uniting directly with 

 acids to form ethers with the elimination of the elements of wa- 

 ter ; the aldehydes, which are formed at the expense of the alco- 

 hols, with the loss of hydrogen, among which are the essence of 

 bitter almonds and the essence of cinnamon; the acids, like 



