PHILOSOPHICAL SOCIETY OF WASHINGTON. 147 



plant, whether we decompose water from the Indian oceau or from 

 Arctic snow-flake, whether we inspect with curious eye the light 

 from sun, or star, or from remotest nebulas at opposite confines of the 

 heavens, we find in the spectrum of hydrogen the same fixed lines ; 

 — assuring us that these are truly the reverberations of periods in- 

 cessantly repeated alike in every molecule of this particular ele- 

 ment.* Taking this — the lightest of all known molecules, (Prout's 

 fundamental unit of chemical equivalency,) we have within the 

 single molecule the widely separated lines of four distinct periodi- 

 cities, or atomic orbits : — the red line " C " (a) of 456 billion revo- 

 lutions per seeond, — the greenish blue line " F " (/?) of 615 billion 

 revolutions, — the blue line near " G " (y) of 689 billion revolutions, 

 and the violet line " h " (8) of 729 billion revolutions. As no form 

 of either reciprocating or orbital movement could possibly be main- 

 tained without an equal and opposite re-action, there must neces- 

 sarily exist here at least eight independent atoms. But it seems 

 wholly improbable that each of these systems of motion should 

 comprise but a single couple of atoms : and it is still more improb- 

 able that either these periods, or even the numerous additional ones 

 disclosed in the secondary spectrum of hydrogen, represent all the 

 atomic motions within its molecule, in view of the necessary imper- 

 fection of the optical record, and the fact that this embraces less 

 than the third, and possibly not more than one-fourth of the whole 

 actinic spectrum. 



Physical Complexity of the Molecule. — We are therefore justified 

 in believing that the most elementary of chemical molecules is a 

 wonderfully complex system, comprising an unknown number of con- 

 stituent units, held together by dynamic bonds whose nature we can 

 neither guess nor conceive ; and thus the atom of Newton and of 

 Dalton has been carried downward far beyond the horizon of action 

 at which they had imagined it — probably even to a second order of 

 diminished magnitude. 



The relations between the translatory motion of the integral gase- 



*'• The same kind of molecule — say that of hydrogen — has the same set 

 of periods of vibration, — whether we procure the hydrogen from water, 

 from coal, or from meteoric iron ; and light having the same set of periods 

 of vibration comes to us from the Sun, from Sirius, and from Arcturus." 

 J. Clerk Maxwell. (Encyclopced. Brit. 1875: art. "Atom," vol. Ill, p. 

 48.) 



