256 Velocity of Light. 



that I doubt whether it will ever be undertaken. It has oc- 

 curred to me, that the final step would be a thorough anato- 

 mical study of the species found in the cave, with extensive 

 comparison of allied species, found elsewhere — next, an in- 

 vestigation of the embryology of all of them, and when fully 

 prepared by such researches, an attempt to raise embryos, 

 of the species found in the cave, under various circumstances, 

 different from those, in which they are naturally found at 

 present. 



If physical circumstances ever modified organized beings, 

 it should be easily ascertained here. For my own part,Jhow- 

 ever, I think that the blind animals of the cave would only 

 show organs of vision during their embryonic state, in con- 

 formity with the normal development of the respective types 

 to which they belong, and that even when placed under a 

 moderate influence of light, incapable of injuring them, but 

 sufficient to favour the growth of their eyes in the allied 

 species provided with them, the young of those species pe- 

 culiar to the cave would gradually grow blind, while the 

 others would acquire perfect eyes ; for I am convinced, from 

 all I know of the geographical distribution of animals, that 

 they were created under the circumstances in which they 

 now live, within the limits over which they range, and with 

 the structural peculiarities which characterise them at the 

 present day. But this is a mere inference, and whoever 

 would settle the question by direct experiment, might be 

 sure to earn the everlasting gratitude of men of [science. 

 And here is a great aim for the young American naturalist 

 who would not shrink from the idea of devoting his life to 

 the solution of one great question. — American Journal of 

 Science and Arts, vol, xi., No. 31, 2d Series, p. 127. 



Velocity of Light. By Humboldt. 



On the subject of the velocity of light, and the probability that 

 it requires a certain time for its propagation, we find the earliest 

 view expressed by Francis Bacon, in the second book of the No- 

 vum Organum. He speaks of the time required by a ray of light to 



