Sronsy—Of the Kinetic Theory of Gas. 373 
scale, the ten-thousandth of a second of time grows to be an 
immense duration, extending to 1900 years. The number of 
struggles to be encountered by each molecule in the ten-thousandth 
of a second, is accordingly the same as the number of days in the 
whole Christian Era, from the birth of Christ down to the end of 
the present century. If something can be done during the 20 
minutes that one of the struggles may last, how great a task 
might be accomplished by such an enormous succession of them. 
It must be borne in mind, too, that these encounters are not mere 
repetitions of one another, but that each has its own definite inci- 
dents. Moreover, all this is what occurs in the experience of one 
individual molecule, so that we must multiply it by something 
like a thousand millions, in order to sum up what may be accom- 
plished by all the encounters of all the molecules within one cubic 
micror! of gas in the ten-thousandth part of a second, and that we 
may in some degree understand how it comes to pass that oppor- 
tunity is afforded in nature for accomplishing work which requires 
rare collocations of conditions that can but seldom emerge. Such is 
Nature’s real laboratory—events in inconceivable numbers, the 
whole phantasmagoria of these innumerable events changing every 
instant down to its minutest details with inconceivable rapidity, the 
changes in most cases kept within limits, but in some exploring 
every part of a wide range: it is thus that those wonderful opera- 
tions are carried on, which issue in the astonishing results that lie 
everywhere in such profusion around us. We seem almost to get 
an obscure and partial glimpse of how, in organic nature, tasks of 
the most unlikely kind are accomplished, through the needful 
streets may stand for the intervals at which the representatives of the molecules are to 
be spaced asunder at starting. 
In this model we have applied so much more magnification to time than to space, 
that all the velocities come out 60,000 times slower than in nature. Accordingly our 
animated molecules must be conceived of as quietly gliding along the journeys 
they have to make between their encounters; for the mean duration of a journey is to 
be a day, and the average speed must accordingly be only half a metre per minute— 
on the supposition that our model is to represent what occurs in gas as dense as air and 
at its temperature and pressure. 
A model of this kind is not without its use, if it were only as a means by which we 
can gain a lively perception of how considerable the events going on within the mole- 
cules may be when compared with the motions of translation of the molecules. 
1 There are 70 or 80 cubic microns in the volume of each of the small disks in 
human blood. 
