244 report — 1879. 



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 

 treat distance from their real causes. We are accordingly still far beyond the 

 rano-e of the exact sciences. Most of the great discoveries of biological science 

 have been made by estimating the general drift of what is taught by a vast num- 

 ber of particular facts. This, it will be observed, is a kind of reasoning that 

 is necessarily more or less inexact, 1 and, as a consequence, it is one which requires 

 wide intellectual training and great experience and tact to handle it with safety. 

 When the investigator has brought these qualifications to his task, astonishing 

 progress has been made in these sciences : without 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 effected. It is here that exact reasoning finds a predominant 



place. 



The study of the physical sciences has been remitted by the British Association 

 to its first two sections, chemistry being assigned to Section B, and the rest of the 

 physical sciences to Section A. Accordingly, Section A includes the whole range 

 of mathematics, along with the study of the conditions of rest and motion in that 

 part of matter which is endowed with mass, and of the phenomena of sound, heat, 

 lio-ht, and electricity, with the applications of these abstract sciences in molecular 

 physics and to astronomy, crystallography and meteorology. 



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 

 which I have enumerated exact reasoning prevails, and on this account they are 

 frequently classed together as the exact sciences. 



The process of investigation in the exact sciences is fundamentally one in all 

 cases. It has been well described by Mill in the third book of his ' Logic' Never- 

 theless, 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 is because there exists a practical distinction 

 separating the investigations of exact science into two well-marked classes when 

 they are viewed, not as they are in themselves, but in their relation to the powers 

 of us human beings. I refer to the distinction between the experimental method 

 or the method of observation, on the one hand ; and the deductive method, or the 

 method of reasoning, on the other. All valid investigations in exact science appeal 

 to what can be directly perceived, and all lead to a conclusion which can be 

 reasoned out from it ; but there are some of these investigations in which the main 

 difficulty consists in making the appeal to the senses, and there are others in which 

 the main difficulty lies in the process of reasoning. 



To contend with these difficulties successfully requires very different qualities 

 of mind and body. In experimental science the powers, principally called into 

 requisition are readiness and closeness of observation, dexterity in manipulation, 

 skill in contriving expedients, accuracy in making adjustments, and great patience. 

 It also requires that the investigator should have an accurate memory of what else 

 he has witnessed resembling the phenomenon under observation, that he should be 

 quick to detect every point of agreement and difference that can be perceived, and 

 be skilful to select those which are significant, and to employ them as materials 

 for prevision to guide his further proceedings. But the strain on the reasoning 



1 Except when the reasoning takes a form in which its strength can be gauged 

 by the doctrine of probabilities. The most satisfactory instance of this is that 

 ' statistical method ' which has proved our most searching tool in molecular physics. 



