INTRODUCTION. 39 



i& we learn more and more how to imvail her secrets, com- 

 prehend the mechanism of the movements of the heavenlv 

 bodies, and estimate numerically the intensity of natural forces. 

 It is true that, properly speaking, the forces of nature can only 

 exercise a magical power over us as long as their action is 

 chrouded in mystery and darkness, and does not admit of be- 

 ing classed among the conditions with which experience has 

 made us acquainted. The effect of such a pov/er is, there- 

 fore, to excite the imagination, but that, assuredly, is not the 

 faculty of mind we v»'ould evoke to preside over the laboriou.s 

 and elaborate observations by which we strive to attain to a 

 knowledo^e of the fjreatness and excellence of the laws of the 

 universe. 



The astronomer who, by the aid of the heliometer or a 

 double-refracting prism,* determines the diameter of planetary 

 bodies ; who measures patiently, year after year, the meridian 

 altitude and the relative distances of stars, or who seeks a tel 

 escopic comet in a group of nebulae, does not feel his imagina- 

 tion more excited — and this is the very guarantee of the pre- 

 cision of his labors — than the botanist who counts the divi- 

 sions of the calyx, or the number of stamens in a flower, or ex- 

 amines the connected or the separate teeth of the peristoma 

 surrounding the capsule of a moss. Yet the multiplied an- 

 gular measurements on the one hand, and the detail of organic 

 relations on the other, alike aid in preparing the way for the 

 attainment of higher views of the laws of the iniiverse. 



We must not confound the disposition of mind in the ob 

 server at the time he is pursuing his labors, with the ulterior 

 greatness of the views resulting from investigation and the 

 exercise of thought. The physical philosopher measures with 

 admirable sagacity the waves of light of unequal length which 

 by interference mutually strengthen or destroy each other, 

 even with respect to their chemical actions ; the astronomer, 

 armed with powerful telescopes, penetrates the regions of 

 space, contemplates, on the extremest confines of our solar 

 system, the satellites of Uranus, or decomposes faintly spark- 

 ling points into double stars differing in color. The botanist 

 discovers the constancy of the gyratory motion of the chara in 

 the greater number of vegetable cells, and recognizes in the 

 genera and natural families of plants the intimate relations 

 of organic forms. The vault of heaven, studded with uebu- 



* Arago's ocular microir Bter, a happy improvement upon Rochon's 

 prismatic or double-refrac /on micrometer. See M. Mathieu's note i» 

 Delambre'a Histoire de V Astronomic au dix-huiticmc Siecle, 18'27. 



