156 Scientific Proceedings, Royal Dublin Society. 
occurs in the few cases in which we can have under observation 
the special consequences of sedected molecular events, instead of, as 
on all ordinary occasions, being only able to measure an average 
outcome from ad/ the molecular events in the portion of matter we 
are examining. 
If some bacilli—those which live on mineral food—obtain their 
whole stock of energy in the way here indicated, it may be pre- 
sumed that all bacilli get at least a part of what they require in 
the same way. 
enclosure are now at a lower temperature than at the beginning, and that the heat 
which they have lost has been converted into mechanical energy. 
It thus appears that the contents of the adiabatic envelope may be regarded as a 
heat-engine, all the parts of which start at a certain temperature, and which yields. 
mechanical energy, while the only other change is that some of its parts are cooled to 
a lower temperature. This contradicts the Second Law of Thermodynamics as formu- 
lated by Lord Kelvin, if we leave the word ‘‘inanimate’’ out of his enunciation. 
His statement of the axiom is:—‘‘ It is impossible, by means of inanimate material 
agency, to derive mechanical effect from any portion of matter by cooling it below the 
temperature of the coldest of surrounding objects.’’ It is legitimate here to omit the 
word ‘inanimate,’ as its insertion merely means that cases of exception to the law 
may be met with in the organic world, and if this be stated it will need to be added 
that cases of exception may also be found among inorganic processes; the correct 
statement being that the law does not apply to individual molecular events, and that 
therefore it need not be obeyed in the cases, whether organic or inorganic, in which 
any observable effect is the outcome of one-sided molecular events. 
It should be borne in mind that the heat of a given portion of matter is the energy 
of motions of and within its molecules; not necessarily of all such motions, but of 
those among them which are capable of restoring energy to the parts of the molecule 
carrying electra (see Stoney on Double Lines in Spectra, ‘‘ Scientific Transactions of 
the Royal Dublin Society,’ Vol. iv., Part xi.) whenever the motion of the electron 
has transferred energy from the molecule to the ether. As fulfilling this criterion 
we are probably to include all irrotational motions within the molecules, and we must 
also include relative motions of the molecules—all of them indeed if time enough be 
allowed for turmoil within a fluid to subside. It does mot include any motion which 
the molecules have in common, as in wind, or in the rotation of a wheel. 
When these circumstances are taken into account, it is obvious that the energy of 
the heat motions of an individual molecule undergoes rapid fluctuations, while there 
may be a definite average of the energy of these motions, whether estimated by what 
happens in an individual molecule over a’ sufficiently long period of time, or when 
estimated by what occurs simultaneously in all the molecules of a body. In other 
words, the motions of an individual molecule do not from instant to instant conform to 
the Second Law of Thermodynamics, although the law may apply both to the average 
of the motions of a single molecule taken over a long period of time, and to the average 
of the simultaneous motions of vast multitudes of associated molecules. As regards 
molecular motions (the motions within a solid, or motions within a fluid that do not 
produce currents in the fluid), the millionth of one second is a long period. 
