COMETS. 91 



Gioja, and the great grey plain near Endymion, which 

 exceeds, in superficial extent, the Mare Vaporum. Three- 

 sevenths of the moon's surface are at all times concealed 

 from the earth, and must always remain so, unless new 

 and unexpected disturbing forces are brought into action. 

 These cosmical relations remind us involuntarily of 

 nearly similar ones in the intellectual world, where, in 

 the domain of deep research and of meditation on the mys- 

 terious elaborations of nature, and on primeval creation, 

 there are regions similarly turned from our view and appa- 

 rently unattainable, of which a narrow margin has for 

 thousands of years presented itself, from time to time tc 

 the human race, glimmering now in true, now in uncertain 

 light. 



Having thus considered, as products of a single tan- 

 gential impulse, and closely connected with each other 

 by mutual attraction, the primary planets, their satellites, 

 and the concentric rings which belong to one of the 

 outermost planets, we have still to notice, among 

 the cosmical bodies which revolve around the sun in 

 paths of their own, and receive light from him, the 

 unnumbered host of comets. If we estimate according to 

 the rules of the calculus of probabilities, the equable dis- 

 tribution of the paths of these bodies, the limits of their 

 perihelia, and the possibility of their remaining invisible to 

 the inhabitants of the earth, their possible numbers 

 will be an amount of myriads astonishing to the irna^ 

 gination. Kepler, with his characteristic liveliness of expres- 

 sion, said, even in his day, " there are more comets in space 

 than fishes in the ocean/' As yet, however, we hardly 



