INTRODUCTORY LECTURE ON EXPERIMENTAL PHYSICS. 



anger and passion, malice and envy, fury and madness; the student of science, 

 though he is obliged to recognise the powerful influence which these wild forces 

 have exercised on mankind, is perhaps in some measure disqualified from pursuing 

 the study of this part of human nature. 



But then how few of us are capable of deriving profit from such studies. 

 W cannot enter into full sympathy with these lower phases of our nature 

 without losing some of that antipathy to them which is our surest safeguard 

 against a reversion to a meaner type, and we gladly return to the company of 

 those illustrious men who by aspiring to noble ends, whether intellectual or 

 practical, have risen above the region of storms into a clearer atmosphere, where 

 there is no misrepresentation of opinion, nor ambiguity of expression, but where 

 one mind comes into closest contact with another at the point where both 

 approach nearest to the truth. 



I propose to lecture during this term on Heat, and, as our facilities for 

 experimental work are not yet fully developed, I shall endeavour to place before 

 you the relative position and scientific connexion of the different branches of the 

 science, rather than to discuss the details of experimental methods. 



We shall begin with Thermometry, or the registration of temperatures, and 

 Calorimetry, or the measurement of quantities of heat. We shall then go on 

 to Thermodynamics, which investigates the relations between the thermal pro- 

 perties of bodies and their other dynamical properties, in so far as these relations 

 may be traced without any assumption as to the particular constitution of these 

 bodies: 



The principles of Thermodynamics throw great light on all the phenomena 

 of nature, and it is probable that many valuable applications of these principles 

 have yet to be made ; but we shall have to point out the limits of this 

 science, and to shew that many problems in nature, especially those in which 

 the Dissipation of Energy comes into play, are not capable of solution by the 

 principles of Thermodynamics alone, but that in order to understand them, we 

 are obliged to form some more definite theory of the constitution of bodies. 



Two theories of the constitution of bodies have struggled for victory with 

 various fortunes since the earliest ages of speculation : one is the theory of a 

 universal plenum, the other is that of atoms and void. 



The theory of the plenum is associated with the doctrine of mathe- 

 matical continuity, and its mathematical methods are those of the Differential 



