A Theory of Ferments and Their Action. 
29 
tremors equal in rapidity to those of light and radiant heat. To a 
mind coming freshly to these subjects the numbers with which scien- 
tific men here habitually deal must appear utterly fantastical; and yet 
to minds trained in the logic of science they express most sober and 
certain truth. The constituent atoms of molecules can vibrate to and 
fro millions and millions of times in a second. The waves of light and 
radiant heat follow each other at similar rates through the luminiferous 
ether. Further, the atoms of different molecules are held together with 
degrees of varying tightness — they are timed, as it were, to notes of 
different pitch. Suppose, then, that the light waves or heat waves 
impinge upon an assemblage of such molecules, what may be expected 
to occur? The same as when a piano is opened and sung into. The 
waves of sound select the strings which respectively respond to them — 
the strings, that is to say, whose rates of vibration are the same as their 
own. Of the whole series of strings these only sound. The vibratory 
motion of the voice imparted first to the air is taken up by the strings. 
It may be regarded as absorbed , each string constituting itself thereby 
a new center of motion; thus also as regards the tightly locked atoms 
of molecules on which waves of light or heat impinge. Like the wave 
•of sound just adverted to, the waves of ether select those atoms whose 
periods of vibration synchronize with their own periods of recurrence, 
and to such atoms they deliver up their motion. It is thus that light 
and radiant heat are absorbed. 
“I have spoken of molecules being wrecked by a moderate amount 
of heat of the proper quality; let us examine this point for a moment. 
Let a quantity of the vapor of nitrite of amyl be introduced into a 
wide glass tube along its axis. (Prior to the entry of the beam, the 
vapor is invisible as the purest air.) When the light enters, a bright 
eloud is immediately precipitated on the beam. This is entirely due 
to the waves of light, which wreck the nitrite of amyl moleucles, the 
products of decomposition forming innumerable liquid particles which 
constitute the cloud. Many other gases and vapors are acted on in a 
similar manner. Now the waves that produce decomposition are by no> 
means the most powerful of those emitted by the sun. It is, for example,, 
possible to gather up the ultra-red waves into a concentrated beam, and 
to send it through the vapor like a beam of light. But, though pos- 
sessing vastly greater energy than the light waves, they fail to produce 
decomposition. Hence the justification of the statement already made,, 
that a suitable relation must subsist between the molecules and the 
waves of ether to render the latter effective. 
“I have stated, without proof, that where absorption occurs the mo- 
tion of the ether waves is taken up by the constituent atoms of the 
molecules. It is conceivable that the ether waves, passing through an. 
