THE HERSCHELS AND THE STAR-DEPTHS. 13 



And here let us pause for a moment to endeavour to 

 realize the fact that more than five thousand of these 

 clouds exist within the range of telescopic vision. The 

 number of stars visible to the unaided eye in the 

 whole heavens is about five thousand that is, on a 

 dark and clear night average eyesight can recognize 

 about 2,500 stars of different orders of brightness. 

 Now suppose that all the stars were suddenly destroyed, 

 the nebulae alone being left, and that at the same time 

 our powers of vision were suddenly increased to such 

 an extent that we could see all objects visible in the 

 telescopes with which the Herschels surveyed the 

 heavens. Then we should see about as many faint 

 cloud-like specks of light as would correspond to the 

 number of stars we now see. And if, further, the 

 defining powers of the Herschelian telescopes could be 

 given to us, we should recognize in these cloud-like 

 specks all the various orders into which the Herschels 

 divided the nebulae. Here we should see straggling 

 clusters very little condensed in their central portions, 

 there globular clusters so rich in stars as to shine with 

 unspeakable glory insomuch that it has been well 

 remarked of some of them that no one who beholds 

 them for the first time in a telescope of adequate 

 power can refrain from a shout of rapture. In some 

 regions the oval nebulas, close set with stars or wholly 

 irresolvable, would be seen, in others spiral and ring 

 nebulae, the strange forms of the ' dumb-bell nebula,' 

 the c crab nebula,' the ' key,' the ' flight of wild ducks,' 

 nebulous stars, and the planetary nebulae, shown under 



