1022 Dynamic Theory. 



But have we any warrant for assuming gravity to be perpetual and 

 therefore an original and necessary affection of matter? The alterna- 

 tive to this assumption is that it is an acquired affection like the mag- 

 netism of the magnet; and if acquired, then it must be like magnetism, 

 the result of work done. And so we should reach the important con- 

 clusion that gravitation is the result and expression of work dove on im- 

 ponderable matter. That is, matter previously imponderable receives 

 an energetic impact that sets up in it the motion gravitation, that abides 

 with it thereafter indefinitely, and thus renders it ponderable. But such 

 expressions as perpetual, indefinite, permanent, &c. , are after all only 

 relative. A permanent magnet will wear out in time, and the product 

 of any work must in the nature of things be liable to become undone. 

 That which has a beginning is liable to have an ending. And if gravi- 

 tation is a result of conditions and the expenditure of work, it is not 

 inconceivable that the work may in time become undone and matter 

 again become imponderable. 



But how can we conceive of work being done on imponderable mat- 

 ter? We certainly have no experience of anything of the sort, but 

 still I believe we may conceive of matter possessing rigidity and elastic- 

 ity, and consequently resistance without ponderability. Such a body 

 might receive an attack and be affected by it, but it is difficult to see 

 how such a body could make an attack. 



A conception which appears to satisfy the conditions of original ex- 

 istence is that of matter in an extremely attenuated condition, yet pos- 

 sessing rigidity and elasticity, and endowed with a certain quantity of 

 motion. From this state of things there would be differentiations in- 

 tensifying and specializing motion in some parts, and reducing it in 

 others, so that we should get matter endowed with energy in different 

 quantities, and becoming ponderable in different degrees. 



The least ponderable remains as ether, and becomes the vehicle for 

 the transportation of the energy arising from the arrest of the motions 

 of the matter endowed with weight. The substance ether is not to be 

 understood as of uniform constitution everywhere, but it differs in den- 

 sity, being more rare in the interplanetary and interstellar spaces, and 

 more dense in the intermolecular spaces, and in the close vicinity of 

 ponderable bodies. There can be little doubt that many of the forms 

 and tones of the various molecular energies depend upon these local 

 conditions of the ether as to density, contiguity to other matter, free- 

 dom, confinement in the interstices, or intermolecular spaces of ponder- 

 able bodies. It is the movements of the condensed ether under differ- 

 ent conditions in the different bodies, machines, and organs with which 

 it becomes involved, that constitute the phenomena of gravity, electric- 

 ity, magnetism, chemism, heat, light, sound, vitality, nerve action, 

 sensation and mentality. 



