14 



In the early years of the present century, optical science re- 

 ceived a powerful impulse from the labors of Dr. Thomas Young, 

 who made the important discoveiy of the interference of light, and 

 gave to double refraction a rational theory by advancing a plau- 

 sible hypothesis of the propagation of light through an elastic 

 medium in a manner not contradictory to any of the well-known 

 facts and laws of dynamics. 



Geology, too, was not without its zealous cultivators. In 1788 

 Hutton published his celebrated " Theory of the Earth," in which, 

 according to Lyell, may be found the germ of the metamorphic 

 theory. Scientific geology in England owes its existence to Wil- 

 liam Smith, who, between the years 1790 and 1815, made a labori- 

 ous examination of different strata in Great Britain, and finally 

 published the first complete geological map that ever appeared. 

 In 1807 was formed the London Geological Society, the mem- 

 bers of which early began with untiring industry to collect the 

 facts relative to the structure of the earth's crust. Owing to the 

 assiduous and intelligent labors of John Hunter, comparative 

 anatom} r , in the last quarter of the eighteenth century, became, 

 for the first time, in Great Britain, a science of importance. In 

 astronomical science many important facts were discovered and 

 recorded. Maskelyne, in 1790, published an admirable catalogue 

 of the stars, while Sir William Herschel, between 1799 and 1820, 

 may be said to have recreated astronomy and enlarged our views 

 of the immensity of space by his astounding discoveries. 



In the mean time, science was steadihy though less rapidly un- 

 folding its fair proportions in various parts of Europe. The inte- 

 gral calculus and analytical mechanics were greatly improved 

 between 1727 and 1783 by Euler, the celebrated Swedish geometer. 

 In Germany, astronomy was cultivated from 1779 to 1815 with 

 signal industry and success by the physician Olbers, who, besides 

 discovering several of the asteroids, published an improved method 

 of calculating the orbits of comets. During this period, Werner, 

 in Germany, and Pallas, in Russia, made many important contri- 

 butions to geological science. By the publication, in 1774, of his 

 short but very remarkable " Treatise on the Characters of Minerals," 

 Werner accomplished for the terminology of mineralogy what the 

 " Philosophia Botanica" of Linnaeus had done for that of botany 

 nearly a quarter of a century before. Moreover, his celebrated 

 ' Classification and Description of Mountains," which appeared in 



