SUMMARY OF FOUR CENTURIES OF SCIENCE. 275 



AND ELECTRICITY," the same period has seen the progress 

 of Mechanics as such, and, as a consequence, the far- 

 reaching development of machinery, whether it be moved 

 by air, water, hand, steam, or electric labour ; so that, failing 

 the title we have just mentioned, the XlXth century would 

 have been known as the " AGE OF MACHINERY." But this is 

 only a part of what the knowledge of the laws of mechanics 

 has done for us : this knowledge led to the performance 

 of engineering works, the conception of which would have 

 seemed senseless and extravagant in the last century; so 

 that again the XlXth century may claim another title, that 

 of the " AGE OF ENGINEERING." 5. Again, the discovery of 

 further physical laws shall we call them PHYSICO-CHEMICAL 

 LAWS ? conduced to another effect, the powerful use of 

 iron and steel, for which our period deserves the name 

 also of the "AGE OF STEEL." 6. The study of physics, 

 which became the absorbing attraction of genius, conduced to 

 the elucidation of the LAWS OF LIGHT AND SOUND, and, as 

 a consequence, to the comprehension of terrestrial and 

 celestial phenomena, which is one of our greatest triumphs. 

 What rash mind only a couple of generations ago would 

 have ventured to predict that we should ever arrive at 

 the knowledge of the constitution and composition of 

 heavenly bodies ? Yet, the problem has been propounded 

 and solved ! Who could have conceived the possibility of 

 your voice, your speech, your song, your laughter, your 

 sighs being "bottled up," and being reproduced to those 

 who love, admire, and remember you ? Yet, an Edison 

 has achieved that miracle ! Who would have thought we 

 could have a picture of a ball-room, or a battlefield, or 

 the remotest regions of space in a few moments? Yet, 

 the photographer does this with faultless accuracy. 7. 

 One of our difficulties, when we wish to gauge the XlXth 

 century, is that it is impossible to say, even after medita- 

 tion, the thing in which the age is greatest. If, being 

 impressed by the power of steam and electricity and the 

 applications of them, we declare them to be the main 

 points, we are met by the claims of the Engineer, the 

 claims of the Physicist, the claims of the Chemist, each 



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