lviii 



examined and compared with the experience and observation of the pre- 

 sent. Even then years of seemingly unrewarded labor, in almost impene- 

 trable darkness, sometimes ensue ; but such stores of facts are at last 

 accumulated that she suddenly ushers us into the glorious presence of a 

 new-born day. In its pure light the mists which hung over our vision 

 melt away, and we see revealed some grand law of nature hitherto unre- 

 cognized. Such, for instance, was the law of gravitation, discovered by 

 Sir Isaac Newton, and by which the movements of the heavenly spheres 

 are explained to us. The development of the theory of the conservation 

 of matter, and the correlation of forces, is another illustration of the dis- 

 covery of, perhaps, a still grander truth; one which Faraday pronounces 

 " the highest law in physical science which our faculties permit us to per- 

 ceive." 



Indeed, some of the results of scientific inquiry have been so amazing, 

 that the powers of the human mind seem almost elevated by them to the 

 verge of omnipotent wisdom. 



The discoveries in Astronomy are especially calculated to raise our con- 

 ceptions of the power of man's intellect to a degree that is well nigh im- 

 pious. Fortunately, however, for our humility, that department of science, 

 more perhaps than all others, is best calculated also to elevate, to the 

 highest possible point, our ideas of the power and wisdom of the Creator. 

 What grander illustration, for example, of the wonderful power of intel- 

 lect can be imagined than that exhibited in the discovery of the planet 

 Neptune? 



Studying the perturbations of the planet Uranus in its orbit, two emi- 

 nent mathematicians, Leverrier and Adams, were led, each unknown to 

 the other, to investigate their cause. They knew that the attraction of 

 gravitation could alone account for these irregularities, and they believed 

 the inducing force was an unknown planet. They had nothing but the 

 eccentric orbit of Uranus and its mass as the data by which to find the 

 orbit, and the place in that orbit of the disturbing body. Yet before that 

 unknown world, ninety-four times greater in bulk than this earth, had 

 been recognized by human eye, the equations of Leverrier enabled him 

 to track its majestic sweep around the distant verge of planetary 

 space with such unerring certainty, that he was enabled to indicate 

 almost the exact place in the firmament in which it was to be discovered. 

 He wrote to Galle, in Berlin, that at that date it could be found in a certain 

 part of the heavens. The very first night after his friend received this 

 letter, he turned the telescope in the observatory of Berlin as directed by 

 Leverrier, and the mighty planet stood triumphantly revealed, within a 

 single degree of the place indicated. 



Sometimes scientific discovery pauses in apparent hopelessness in cer- 

 tain fields for centuries; in others it advances with slow but constant 

 pace, each step being due to the successive or united labors of many 

 minds; whilst in others, again, it moves onward with strides so rapid and 

 startling as to challenge the admiration of the world. Some of the 

 phenomena of electricity and magnetism were known for ages before 



