1871.] Molecules, Ultimates, Atoms, and Waves. 465 



force must be looked to, as that which countervails the 

 repulsive power of the ethereal particles to so great an 

 extent as 1-7246^ part of its amount. 



The phenomenon might be explained by supposing the 

 existence of some special repulsive energy, as between the 

 ethereal particles and the ultimates of hydrogen, rendering 

 these, in proportion to their specific gravity, conspicuous 

 beyond all others in their power of driving the ethereal par- 

 ticles into closer mutual proximity. An alternative and 

 better explanation, however, is furnished by the supposition 

 that the ultimates of hydrogen are not simple homo- 

 geneous masses, but are really compounded of numerous 

 and diverse more minute atoms, held together by a force 

 greatly exceeding that of gravity, or even those of ordinary 

 cohesion and chemical attraction. For to prevent such 

 atoms from passing into absolute contact, and to admit 

 of their being thrown into a state of vibration, the ether 

 separating them must be compressed to such an extent as 

 to render it capable of balancing the force by which the 

 atoms are held in such close mutual proximity. Thus, 

 making a small allowance for the force of gravity, we 

 obtain as a measure of the attractive force by which the 

 atoms constituting the ultimate of hydrogen are held 

 together, about 1-7240t.l1 part of the total repulsive energy 

 which the ethereal particles exert one upon another. 



Now the observations on the spectrum tend to render the 

 latter explanation of the extraordinary power of hydrogen 

 in compressing the ether the more probable of the two. 

 These show that hydrogen can either generate or interrupt 

 ethereal waves of four different lengths and periods. They 

 are as under — the lengths being stated in billionths of 

 an inch, and the periods in parts of the billionth of a 

 second : — 



Length. Period. 



Wave producing the line c, 25,852,720, one 453rd. 



Wave producing the line f, 19,149,930, one 612th. 



Wave producing a line near G, 17,098,700, one 685th. 



Wave producing a line near H, 16,157,500, one 725th. 



It being extremely improbable that there are four distinct 

 sorts of hydrogenous ultimates, capable of either genera- 

 ting or absorbing those four sorts of vibrations, the most 

 simple, if not the only, explanation of the phenomenon 

 appears to be, that each ultimate consists of four diverse 

 sorts of atoms, to which those four different vibrations are 

 to be attributed. 



It would be difficult to imagine any other mode of their 



