528 THE POPULAR SCIENCE MONTHLY. 



aggi'egations, at the same time they do not conflict with such a modi- 

 fication of that hypothesis as assumes the actual magnitude of these 

 units so far reduced as to be practically infinitesimal. They only 

 declare but this they do in the most emphatic manner that this 

 reduction must not be so far continued as to make the ultimate atom 

 equal to zero, in the sense of absolute nullity. 



On this view, which is by no means a new one, of the ultimate 

 constitution of matter, the units of the so-called chemical elements, 

 even of those having the smallest atomic weights, may themselves be 

 of a relatively high order of aggregation or organization, below which 

 many degrees may exist in which the molecules are too minute to 

 form bodies which the senses can in any manner detect. The inter- 

 stellar ether may be explained as constituting one of the highest of 

 these degrees, yet not high enough to form matter such as to be visibly 

 subject to the law of gravitation. The nebulae present the evidence 

 of the lowest form of such so-called " ponderable matter," and these 

 may be supposed to be the result of a gradual development resulting 

 from the successive recompounding of the molecular aggregates, 

 until they finally acquire a certain influence over one another and tend 

 to molar aggregation, forming the nebular masses. At the outset 

 these aggregates may be supposed to be entirely homogeneous, con- 

 sisting wholly of molecules of the same degree of aggregation, but 

 they soon differentiate into several distinct kinds of matter. These 

 are the gases which the spectroscope reveals in some of the nebulae. 

 They have molecules of low atomic weights and remain gaseous at all 

 temperatures artificially producible. This process of evolution, which 

 is the same which we have seen to go on in all the well-known forms 

 of matter, would seem also to continue throughout the history of the 

 nebulaB and the organization of resultant planetary systems, developing 

 many additional forms of matter, likewise characterized by the in- 

 creasing mass of their molecules. 



What the properties of those molecular aggregates may be whose 

 activities can not be revealed to sense, is of course unknown. Con- 

 jecture even as to the probable number of degrees of aggregation 

 from the ultimate atom to the supposed atom of hydrogen would of 

 course be idle. But that such forms exist far down upon this inac- 

 cessible plane, having definite shapes, sizes, and activities, we are 

 strongly led to assume, both by the facts already stated and by others 

 presently to be set forth. 



Passing over these lower stages, therefore, whose study belongs to 

 the future of human science, or to possible beings endowed with finer 

 faculties, and which may be said to belong to the domain of transcen- 

 dental chemistry, we finally arrive at a class of aggregates of great, 

 stability, but which, though still so minute that they can only be 

 perceived when accumulated into masses, have nevertheless been 

 studied in their free state by means of the various phenomena to 



