Stonsy— The known part of Nature's Work. 95 
game. It must be an unusual experience for a human being 
to be witness to so rare an event. The probability of it is only 
one in 13,060,700,000. Yet so great is the number of molecules 
in a gas, and so frequent their encounters, that some mlions 
of cases occur every second in every cubic micron of the air 
about us, in which an encounter between molecules has taken 
place under conditions as exceptional as the above ; and equally 
unusual events probably occur some thousands of times more fre- 
quently in the encounters between the molecules of two liquids, 
or of a liquid and a solid. It is thus that chemical reactions and 
events in biology can extend over a duration which is appreciable 
by us, even in the case of explosions; the fact being that in all 
such it is their evcessive slowness from the molecular standpoint 
that has to be accounted for. 
CoNncLUSION. 
No physicist can consult the diagram presented in fig. 6 with- 
out being struck by its resemblance to an absorption band in a 
spectrum. Nature is occupied in working everywhere over the 
entire spectrum; man’s knowledge of her works is confined to what - 
occurs within this one absorption band. How much changed 
would be the aspect under which the human mind would have had 
to view nature, if the position of the absorption band had occupied 
a different place—if, for example, the range of our knowledge 
had been Groups B, C, D, and H, instead of A, B, C, and D; with 
such a full knowledge of molecular objects and events as we now 
enjoy of objects that range from kilems down to microns; 
and with such a lessened knowledge of Group C as we now 
have of planetary events! An equally startling change would 
be made if the range had been shifted the other way: if we had 
no knowledge of microscopic or molecular events, just as we 
now possess none of those which go on within and beyond sub- 
section w of Group D; if at the same time we had only a 
smattering of knowledge about Group C, such as the fragments 
we are now able with difficulty to obtain about Group D, accom- 
panied by some real acquaintance with the immense universe that 
lies beyond Group A. 
Along with these considerations we should ever bear in mind 
