294 POPULAR SCIENCE MONTHLY. 



clothing, the means of combating disease, the means of transportation, 

 the means of producing heat and a great variety of things that con- 

 tribute to his bodily comfort and gratify his esthetic desires. It is 

 not my purpose to attempt to deal with all of these and to show how- 

 science is helping to work out the problems suggested. I shall have 

 to content myself by pointing out a few of the more important prob- 

 lems the solution of which depends upon the prosecution of scientific 

 research. 



First, the food problem. Whatever views one may hold in regard 

 to that which has come to be called 'race suicide,' it appears that the 

 population of the world is increasing rapidly. The desirable places 

 have been occupied. In some parts of the earth there is such a surplus 

 of population that famines occur from time to time, and in other parts 

 epidemics and floods relieve the embarrassment. We may fairly look 

 forward to the time when the whole earth will be overpopulated unless 

 the production of food becomes more scientific than it now is. Here is 

 the field for the work of the agricultural chemist who is showing us 

 how to increase the yield from a given area, and, in case of poor and 

 worn-out soils, how to preserve and increase their fertility. It appears 

 that the methods of cultivating the soil are still comparatively crude, 

 and more and more thorough investigation of the processes involved in 

 the growth of plants is called for. Much has been learned since Liebig 

 founded the science of agricultural chemistry. It was he who pointed 

 out some of the ways by which it is possible to increase the fertility 

 of a soil. Since the results of his investigations were given to the 

 world the use of artificial fertilizers has become more and more general. 



But it is one thing to know that artificial fertilizers are useful and 

 it is quite another thing to get them. At first bone dust and guano 

 were chiefly used. Then as these became dearer, phosphates and 

 potassium salts from the mineral kingdom came into use. 



At the Fifth International Congress for Applied Chemistry, held 

 at Berlin, Germany, last June, Dr. Adolph Frank, of Charlottenburg, 

 gave an extremely interesting address on the subject of the use of the 

 nitrogen of the atmosphere for agriculture and the industries, which 

 bears upon the problem that we are dealing with. Plants must have 

 nitrogen. At present this is obtained from the great beds of saltpeter 

 found on the west coast of South America — the so-called Chili salt- 

 peter — and also from the ammonia obtained as a by-product in the 

 distillation of coal, especially in the manufacture of coke. The use 

 of Chili saltpeter for agricultural purposes began about 1860. In 

 1900 the quantity exported was 1,453,000 tons, and its value was about 

 $60,000,000. In the same year the world's production of ammonium 

 sulphate was about 500,000 tons, of a value of somewhat more than 

 $20,000,000. Of these enormous quantities about three quarters finds 



