108 ASTRONOMICAL HISTORY. 



infinite space and finite bodies), bodies would never cohere : 

 therefore on account of coinfinity of matter and space a 

 vacuum is necessarily compressed into certain limits ; which 

 seems to have been his opinion, truly and accurately un 

 derstood ; in other words, that certain limits must be set 

 to the developement or expansion of bodies through the 

 permeating vacuum ; not granting a vacuum apart, or space 

 unreplenished with body. But if there cannot be admitted 

 in the system, a vacuum of the nature of a solution of con 

 tinuity, yet seeing there is found in the parts or portions of 

 the system so extreme a diversity of bodies that they seem 

 to be of different races and countries, there arises a second 

 question which relates to the connection of the system ; it 

 is this, whether pure ether be one entire or unbroken stream, 

 or whether it consist of a variety of contiguous parts ? Now 

 it is no part of our character to subtilize about words : but 

 by a contiguous body we understand one which lies upon, 

 without being amalgamated with, another body. Nor again 

 do we mean some impenetrable or hard superstratum, such 

 as the astronomers in general mean, but one such as fluids 

 exhibit, in the instance of water floating on the top of 

 quicksilver ; oil, of the water ; air, of the oil. For no one 

 can doubt that in the immense expanse of ether there are 

 immense differences in rarity and density, and in many 

 other properties: but granting either, that is a plenum or 

 vacuum, this may equally be the fact. For it is sufficiently 

 certain that not even in the sea itself, the water at the top 

 and at the bottom is of the same consistency and taste ; 

 and, in the air, there is extreme difference between the air 

 contiguous to the earth, and the upper air, and yet it is 

 one entire and unbroken liquid body. The question is 

 therefore brought to this point : whether the differences in 

 the tract of pure air, as it were, insinuate themselves in 

 a continuous stream of imperceptible gradations, or are 

 distributed and arranged into defined and conspicuous 

 limits, where bodies are joined in their locality, which could 

 not be amalgamated, even as among us air lies on water. 

 For to one who considers the matter simply, the whole 

 of that clear and limpid substance in which the globes 

 of the earth and sun are suspended and float, and which, 

 being interposed between those globes, by its quantity 

 and the space which it occupies, exceeds the dimension of 

 the globes, so to speak, innumerable times,- -is a thing- 

 undivided and perfectly united within itself. But to one 

 who looks into nature more correctly, this will plainly 



