136 MODERN SCIENCE READER 



of salicylic acid almost the sole constituent of the fragrant 

 oil of the American wintergreen (Gaultheria procwmbens) . 



The artificial production of such substances was early 

 undertaken, and has tended to increase their use by mak- 

 ing prices lower. A number of perfumes which very 

 perfectly reproduce the odors of various fruits are called 

 fruit-ethers, and their composition has been known for a 

 considerable length of time. They are compounds esters, 

 so called of alcohols, such as ethyl-alcohol, butyl-alcohol 

 and amyl-alcohol, with acetic, butyric and valerianic acids; 

 and they are extensively used in the manufacture of fruit 

 beverages and confectionery for the imitation of all pos- 

 sible fruit aromas. 



Researches into the nature of these few comparatively 

 simple substances comprised at first the whole of our 

 chemical knowledge of the subject, and it was a long time 

 before further information was gained in regard to the 

 complex odorous elements. It seemed at first as if a 

 hydrocarbon, C 10 H 16 , were a common and characteristic 

 constituent of a large proportion of the essential oils; but 

 it was soon discovered that this substance, isolated from 

 the different oils, showed, with the same composition in 

 point of percentage, entirely different physical properties, 

 and above all things did not determine their odor. The 

 essential and very important practical question of the 

 characteristic odorous principle of each volatile oil was 

 thus little advanced and was the chief point of interest in 

 all researches. The investigators were led in the main to 

 observe the oils of similar odor in groups, and to look for 

 them according to their common constituents. For exam- 

 ple, the costly oil of roses, valued sometimes at one thou- 

 sand marks and more per kilo, is unmistakably similar in 

 odor to a very inexpensive oil obtained from a species of 

 East Indian grass, Andropogon schoenanthus, and also to 

 geranium oils distilled from different species of Pelargon- 

 ium, in Spain and North Africa, particularly at Reunion. 

 This resemblance was well enough known to the old 



