258 WRITINGS OF JOSEPH HENRY. [1846 



effect of transmission of mere force, (without intervening 

 matter,) such as that of attraction and repulsion, is evident 

 from the fact that these actions require no perceptible time 

 for their transmission to the most distant part of the solar 

 system. If the sun were at once to be annihilated the planet 

 Neptune would, at the same instant begin to move in a tan- 

 gent to its present orbit. Also, the phenomena of electricity 

 and magnetism involve the consideration of time ; the dis- 

 charge of the former through a copper wire is transmitted 

 with about the velocity of light, and the development of 

 the latter in an iron bar is attended with a change in the 

 ponderable molecules of the metal which requires time for 

 its completion. 



According to the foregoing rules, we may assume with 

 Newton, the existence of one kind of matter diffused through- 

 out all space, and existing in four states, namely, the sethe- 

 rial, the aeriform, the liquid, and the solid. This method of 

 presenting the atomic hypothesis of the constitution of mat- 

 ter, may at first sight appear startling ; but on a little re- 

 flection, it will be found a necessary consequence of the 

 attempt to explain the mechanical phenomena of matter by 

 an assemblage of separate atoms. It may be objected to the 

 assumption of one kind of matter that the fact of the im- 

 ponderable nature of light, heat, electricity and magnetism 

 require at least two kinds of matter ; but if we adopt the 

 theory of undulation, the phenomena of the "imponderables" 

 (as they are called) are merely the results of the motions of 

 the atoms of the setherial medium combined in some cases 

 with the motion of the atoms of the body ; and since the vi- 

 brations of the atoms of a mass of matter do not increase the 

 attraction of the earth on the mass, an increase of tempera- 

 ture in a body cannot change its weight ; and also because 

 the setherial medium fills all space, a portion of this 

 medium can no more exhibit weight than a quantity of air 

 when weighed in the midst of the atmosphere. 



The points here noticed, relate merely to the fundamental 

 conceptions of the corpuscular or atomic constitution of 

 matter, and not to the arrangement of the atoms into sys- 



