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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 mischievous 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 service; 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 inconvenience 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 making 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 abandonment 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. CHARLES HENRY.

A CONSIDERABLE number of mineral compounds are odorous. It is enough to mention, as illustrations of the fact, the sulphureted hydrogen odor of rotten eggs, and the scent of hydrocyanic 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 syntheses 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 water; the aldehydes, which are formed at the expense of the alcohols, with the loss of hydrogen, among which are the essence of bitter almonds and the essence of cinnamon; the acids, like