A GLASS OF WATER. 657 



few centuries later, however, events occurred which were originated 

 and put upon the scene by means of the art of printing, and which 

 greatly diminished the blessings of the invention on account of the al- 

 most total destruction of national prosperity during the Thirty Years' 

 War. The art itself meanwhile had not improved. The prints of those 

 times are poor and wretched compared with the excellent works of 

 Guttenberg. The importance of the art by far exceeds its intellectual 

 merit. Many inventions have since been made, which involve far 

 higher intellectual endowments than the invention of printing. The 

 Jacquard loom, the stocking-frame, the carding-machine, the watch, the 

 chronometer, and other inventions, unquestionably involve rarer gifts 

 of combination and executive force ; yet, as regards influence, none of 

 them can even remotely be compared with the printing-press ; none 

 would at that time have come to light without the press. 



This vast capital handed down to us by former generations, modern 

 humanity has immeasurably increased, even doubled and trebled. The 

 inventions and discoveries mentioned thus far are fully known, as to 

 their immense bearing upon the direction of human life. 



In addition to these, let us record two events of the second half of 

 the last century, which, more promptly and thoroughly than even any 

 of the preceding, changed the entire social conditions of humanity : 

 one an invention, that of the steam-engine ; the other a discovery, that 

 of oxygen. 



The importance of the steam-engine requires no comment. Man 

 derives power from the rays of the sun which were stored up as carbon 

 in the vegetable kingdom from time immemorial. The steam which to- 

 day gushes from the locomotive is an equivalent of the rays that de- 

 composed the carbonic acid of the huge marine plants of those early 

 periods, and accumulated the carbon as a source of power a sleeping 

 affinity, a lifted weight. In combining this carbon again with oxygen, 

 Ave produce precisely as much heat as disappeared during the growth 

 of those plants. The steam generated by this heat we allow to push 

 against a movable obstacle, and to this obstacle we attach the resist- 

 ances to be overcome a train of cars, a number of looms or hammers, 

 grindstones or rolls. The power is neither given us nor is it generated. 

 It disappears with the wood or the coal. 



The discovery of oxygen has an altogether different importance. 

 We are confronted by an apparently insignificant fact which Destiny 

 seemed for a time to have permanently assigned to the chemist's labo- 

 ratory. It was on the 1st of August, in 1774, that Priestley, an Eng- 

 lish clergyman and a naturalist, for the first time performed the 

 celebrated experiment which up to the present day is repeated in 

 nearly every course of lectures on experimental chemistry. He heated 

 red oxide of mercury in a small glass retort, and obtained an invisible, 

 colorless gas together with drops of liquid mercury. To collect the 

 gas he employed the same means which we still use to-day. He took 

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