RELATIONS OF SCIENCE TO THE PUBLIC WEAL. 239 



ence for good or evil in the economy of the world. These micro-or- 

 ganisms, the latest contribution to our knowledge of air, perform great 

 analytical functions in organic nature, and are the means of converting 

 much of its potential energy into actual energy. Through their action 

 on dead matter the mutual dependence of plants and animals is secured, 

 so that the air becomes at once the grave of organic death and the 

 cradle of organic life. No doubt the ancients suspected this without 

 being able to prove the dependence. Euripides seems to have seen it 

 deductively when he describes the results of decay : 



" Then that which springs from earth, to earth returns, 

 And that which draws its being from the sky 

 Rises again up to the skyey height." 



The consequences of the progressive discoveries have added largely 

 to our knowledge of life, and have given a marvelous development to 

 the industrial arts. Combustion and respiration govern a wide range 

 of processes. The economical use of fuel, the growth of plants, the 

 food of animals, the processes of husbandry, the maintenance of pub- 

 lic health, the origin and cure of disease, the production of alcoholic 

 drinks, the processes of making vinegar and saltpeter — all these and 

 many other kinds of knowledge have been brought under the domin- 

 ion of law. No doubt animals respired, fuel burned, plants grew, 

 sugar fermented, before we knew how they depended upon air. But, 

 as the knowledge was empirical, it could not be intelligently directed. 

 Now all these processes are ranged in order under a wise economy of 

 Nature, and can be directed to the utilities of life : for it is true, as 

 Swedenborg says, that human "ends always ascend as Nature de- 

 scends." There is scarcely a large industry in the world which has 

 not received a mighty impulse by the better knowledge of air acquired 

 within a hundred years. If I had time I could show still more strik- 

 ingly the industrial advantages which have followed from Cavendish's 

 discovery of the composition of water. I wish that I could have done 

 this, because it was Addison who foolishly said, and Paley who as un- 

 wisely approved the remark, that "mankind required to know no more 

 about water than the temperature at which it froze and boiled, and 

 the mode of making steam." 



When we examine the order of progress in the arts, even before 

 they are illumined by science, their improvements seem to be the re- 

 sultants of three conditions : 



1. The substitution of natural forces for brute animal power, as 

 when Hercules used the waters of the Alpheus to cleanse the Augean 

 stables ; or when a Kamchadal of Eastern Asia, who has been three 

 years hollowing out a canoe, finds that he can do it in a few hours by 

 fire. 



2. The economy of time, as when a calendering machine produces 

 the same gloss to miles of calico that an African savage gives to a 



