66 THE SEVEN FOLLIES OF SCIENCE 



That this was equivalent to perpetual motion, pure and 

 simple, was obvious even to those who were least familiar 

 with such subjects, though the idea of calling it perpetual 

 motion was sternly repudiated by all concerned the term 

 "perpetual motion" having become thoroughly offensive 

 to the ears of common-sense people, and consequently 

 tending to cast doubt over any enterprise to which it 

 might be applied. 



That liquid air is a real and wonderful discovery, and 

 that for a certain small range of purposes it will prove 

 highly useful, cannot be doubted by those who have seen 

 and handled it and are familiar with its properties, but that 

 it will ever be successfully used as an economical source 

 of mechanical power is, to say the least, very improbable. 

 That a small quantity of the liquid is capable of doing an 

 enormous amount of work, and that under some conditions 

 there is apparently more power developed than was origin- 

 ally required to liquefy the air, is undoubtedly true, but 

 when a careful quantitative examination is made of the 

 outgo and the income of energy, it will be found in this, 

 as in every similar case, that instead of a gain there is a 

 very decided and serious loss. The correct explanation of 

 the fallacy was published in the " Scientific American," by 

 the late Dr. Henry Morton, president of the Stevens 

 Institute, and the same explanation and exposure were 

 made by the writer, nearly fifty years ago, in the case of 

 a very similar enterprise. The form of the fallacy in both 

 cases is so similar and so interesting that I shall make no 

 apology for giving the details. 



About the year 1853 or 1854, two ingenious mechanics 

 of Rochester, N. Y., conceived the idea that by using some 

 liquid more volatile than water, a great saving might be 



