86 Things not generally Known. 



Ham Herschel estimated to be 243 times farther from us than 

 Sirius. Caroline Herschel discovered in the right foot of An- 

 dromeda a nebula of enormous dimensions, placed at an incon- 

 ceivable distance from us : it consists probably of myriads of 

 solar systems, which, taken together, are but a point in the 

 universe. The nebula about 10 west of the principal star in 

 Triangulum is supposed by Sir William Herschel to be 344 

 times the distance of Sirius from the earth, which would be the 

 immense sum of nearly seventeen thousand billions of miles 

 from our planet. 



INFINITE SPACE. 



After the straining mind has exhausted all its resources in 

 attempting to fathom the distance of the smallest telescopic 

 star, or the faintest nebula, it has reached only the visible con- 

 fines of the sidereal creation. The universe of stars is but an 

 atom in the universe of space ; above it, and beneath it, and 

 around it, there is still infinity. 



ORIGIN OF OUR PLANETARY SYSTEM. THE NEBULAR 

 HYPOTHESIS.* 



The commencement of our Planetary System, including the 

 sun, must, according to Kant and Laplace, be regarded as an 

 immense nebulous mass filling the portion of space which is 

 now occupied by our system far beyond the limits of Neptune, 

 our most distant planet. Even now we perhaps see similar 

 masses in the distant regions of the firmament, as patches of 

 nebulae, and nebulous stars ; within our system also, comets, 

 the zodiacal light, the corona of the sun during a total eclipse, 

 exhibit resemblances of a nebulous substance, which is so thin 

 that the light of the stars passes through it unenfeebled and 

 unref meted. If we calculate the density of the mass of our 

 planetary system, according to the above assumption, for the 

 time when it was a nebulous sphere which reached to the path 

 of the outmost planet, we should find that it would require 

 several cubic miles of such matter to weigh a single grain. 

 Professor Helmholtz. 



A quarter of a century ago, Sir John Herschel expressed his 

 opinion that those nebulae which were not resolved into indivi- 

 dual stars by the highest powers then used, might be hereafter 

 completely resolved by a further increase of optical power : 



* The letters of Sir Isaac Newton to Dr. Bentley, containing suggestions for 

 the Boyle Lectures, po-sess a peculiar interest in the present day. " They show" 

 (says Sir Pavid Brewster) "that the nebulnr hypothesis, the dull and dangerous 

 heresy of the age, is incompatible with the established laws of the material uni- 

 verse, and that an omnipotent arm was required to give the planets their posi- 

 tions and motions in spare, and a presiding intelligence to assign to them the 

 different functions they had to perform." Life of Newton, vol. ii. 



