638 British Association. [September, 
encountered by the complexity and remoteness of the effects 
which present themselves for examination, and by a deep and 
unpenetrated obscurity hanging over the interval between them 
and their causes. In order to make any progress even in the 
subordinate task of tracing out the relations of these effedts tc 
one another, the inquirer finds it necessary to venture upor 
hypothesis, and in all metaphysical speculation we sadly miss 
that healthy discipline with which Nature in other branches oi 
science relentlessly refutes our hypotheses if they are wrong 
Here, then, is a region in which the plausible may be mistaken 
for the true ; and it is unfortunately certain that it has some 
times been so mistaken by the ablest human minds. 
The biological sciences treat of all the phenomena of living 
beings except their mental phenomena, which are those which 
lie most remote from their causes. Here the complication is 
less, but it is still too great for the human mind to have yet 
penetrated behind it. We are still occupied with phenomena 
which lie at a great distance from their real causes. We are 
accordingly still far beyond the range of the exadt sciences. 
Most of the great discoveries of biological science have been 
made by estimating the general drift of what is taught by a vast 
number of particular fadts. This, it will be observed, is a kind 
of reasoning that is necessarily more or less inexadt, and, as a 
consequence, it is one which requires wide intelledtual training 
and great experience and tadt to handle it with safely. When 
the investigator has brought these qualifications to his task, 
astonishing progress has been made in these sciences : with- 
out them the reasoning may degrade into being either trivial 
or loose. 
In the rest of the study of Nature we are not embarrassed by 
the phenomena of life, and many mysteries therefore stand aside 
out of our path. Here lies the domain of the physical sciences. 
It is here that the mind of man has best been able to cope with 
the realities of the universe, and in which its greatest achieve- 
ments have been effedted. It is here that exadt reasoning finds 
a predominant place. 
In meteorology, owing to the complication of the materials 
that have to be dealt with, we must have frequent recourse to 
the same kind of reasoning as has been found so effectual in the 
biological sciences; but in the other physical sciences exadt 
reasoning prevails, and on this account they are frequently 
classed together as the exadt sciences. 
The process of investigation in the exadt sciences is funda- 
mentally one in all cases. It has been well described by Mill in 
the third book of his “ Logic.” Nevertheless, it is notorious 
that minds which are well fitted for some branches of physical 
inquiry find difficulty — sometimes insuperable difficulty — in 
pursuing others. It is not every eminent mathematician who 
would have made an equally good chemist, or vice versa . This 
