PREFACE. 



THIS volume on Heat is the third of a series forming a Text-Book 

 on Physics. The first two volumes dealt with the Properties of 

 Matter and Sound, and the succeeding volumes will deal with 

 Magnetism and Electricity, and Light. 



The Text-Book is intended chiefly for the use of students who 

 lay most stress on the study of the experimental part of Physics, 

 and who have not yet reached the stage at which the reading 

 of advanced treatises on special subjects is desirable. To bring 

 the subject within the compass thus prescribed, an account is 

 given only of phenomena which are of special importance, or 

 which appear to throw light on other branches of Physics, and the 

 mathematical methods adopted are very elementary. The student 

 who possesses a knowledge of advanced mathematical methods, 

 and who knows how to use them, will, no doubt, be able to work 

 out and remember most easily a theory which uses such methods. 

 But at present a large number of earnest students of Physics are 

 not so equipped, and the authors aim at giving an account of the 

 subject which will be useful to students of this class. Even for 

 the reader who is mathematically trained, there is some advan- 

 tage in the study of elementary methods, compensating for their 

 cumbrous form. They bring before us more evidently the points 

 at which various assumptions are made, and they render more 

 prominent the conditions under which the theory holds good. 



J. H. P. 



