SCIENTIFIC INVESTIGATION AND rEOGRESS. 295 



application in agriculture. The use of these substances, especially of 

 saltpeter, is increasing rapidly. At present it seems that the successful 

 cultivation of the soil is dependent upon the use of nitrates, and the 

 supply of nitrates is limited. Unless something is done we may look 

 forward to the time when the earth, for lack of proper fertilizers, will 

 not be able to produce as much as it now does, and meanwhile the 

 demand for food is increasing. According to the most reliable estima- 

 tions indeed the saltpeter beds will be exhausted in thirty or forty 

 years. Is there a way out? Dr. Frank shows that there is. In tlie 

 air there is nitrogen enough for all. The plants can make only a 

 limited use of this directly. For the most part it must be in some 

 form of chemical combination as, for example, a nitrate or ammonia. 

 The conversion of atmospheric nitrogen into nitric acid would solve 

 the problem, and this is now carried out. But Dr. Frank shows that 

 there is another, perhaps more economical, way of getting the nitrogen 

 into a form suitable for plant food. Calcium carbide can now be made 

 without difficulty and is made in enormous quantities by the action of 

 a powerful electric current upon a mixture of coal and lime. This 

 substance has the power of absorbing nitrogen from the air, and the 

 product thus formed appears to be capable of giving up its nitrogen 

 to plants, or, in other words, to be a good fertilizer. It is true that 

 this subject requires further investigation, but the results thus far 

 obtained are full of promise. If the outcome should be what we have 

 reason to hope, we may regard the approaching exhaustion of the salt- 

 peter beds with equanimity. But, even without this to pin our faith 

 to, we have the preparation of nitric acid from the nitrogen and oxygen 

 of the air to fall back upon. 



While speaking of the food problem, a few words in regard to the 

 artificial preparation of foodstuffs. I am sorry to say that there is not 

 much of promise to report upon in this connection. In spite of the 

 brilliant achievements of chemists in the field of synthesis it remains 

 true that thus far they have not been able to make, except in very small 

 quantities, substances that are useful as foods, and there is absolutely 

 no prospect of this result being reached within a reasonable time. A 

 few years ago Berthelot told us of a dream he had had. This has to 

 do with the results that, according to Berthelot, are to be brought about 

 by the advance of chemistry. The results of investigations already 

 accomplished indicate that, in the future, methods will perhaps be de- 

 vised for the artificial preparation of food from the water and carbonic 

 acid so abundantly supplied by nature. Agriculture will then become 

 unnecessary, and the landscape will not be disfigured by crops growing 

 in geometrical figures. Water will be obtained from holes three or 

 four miles deep in the earth, and this water will be above the boiling 

 temperature, so that it can be used as a source of energy. It will be 



