356 THE AMERICAN ASSOCIATION FOR 



all-important discovery of the attraction of gravitation, of the 

 laws of planetary motion, of the circulation of the blood, of 

 the measurement of the velocity of light. To the eighteenth 

 century we refer the more important of the earl}'- steps in the 

 evolution of the steam-engine and the foundation of both modern 

 chemistry and electrical science. This completes the list. Count- 

 ing all these inventions and discoveries as separate, we get sixteen. 

 Wallace places the barometer and thermometer under one num- 

 ber, and makes a total of fifteen. 



" In making such a list it is evident that the personal equation 

 of the author undoubtedly needs to be recognized, and different 

 orders of arrangement, even if the elements were the same, would 

 be assigned by different students. At any rate, something like 

 this is the list of what the race has gained in science since it first 

 came to itself up to the year 1800. The greatest steps have cer- 

 tainly all been counted. 



"And now what has the record been since 1800 ? How does 

 the nineteenth century compare with its predecessors? A brief 

 examination will show us that in scientific discovery and pro- 

 gress it is not to be compared with an} r single century, but rather 

 with all past time. In fact, it far outweighs the entire pro- 

 gress of the race from the beginning up to 1800. Counting on 

 the same basis as that which he had previously adopted, Wal- 

 lace finds twenty-four discoveries and inventions of the first class 

 that have had their origin in the nineteenth century against the 

 fifteen or sixteen alread} 7 enumerated of all the past. This is 

 not the proper occasion to review, compare, and set in order the 

 several elements of this glorious list, but let me simply recall to 

 your minds a few of them. 



" Of the same rank with Newton's theory of gravitation, which 

 comes from the seventeenth century, stands out the doctrine of 

 the correlation and conservation of forces of our own century, 

 certainly one of the widest and most far-reaching generalizations 

 that the mind of man has yet reached. Against Kepler's laws 

 from the seventeenth century we can set the nebular theory of 

 the nineteenth. The telescope of the seventeenth is overbalanced 

 by the spectroscope of the nineteenth. If the first reveals to us 

 myriads of suns, scattered through the illimitable fields of space, 

 the second tells what substances compose these suns and main- 

 tain their distant fires, and, most wonderful of all, the direction 

 and the rate in which each is moving. Harvey's immortal dis- 

 covery of the seventeenth centur}' finds a full equivalent in the 



