Proceedings of the British Association. 161 



puted by Mr. Kelland's method in the Phil. Trans. 1838. Thus 

 it was desirable to recompute series 2, by an exact method, and 

 necessary to calculate all the neio and improved results of series 3. 

 This the author has now done, by means of Sir W. R. Hamil- 

 ton's formula, and for the sake of uniformity has included series 1. 

 The results agree perfectly with observation, except in the most 

 highly dispersive cases. But here it is found that if an empirical 

 change be allowed in one of the constants for each medium, a 

 sufficiently close accordance is obtained. 



Prof. Powell also communicated a paper on the refraction of 

 heat^ and one on certain points of the Wave Theory of Light. 



Prof. Whewell gave an abstract of a Report on the present 

 state of our theoretical and experimental knoioledge of the laws 

 of Conduction of Heat, by Prof. Kelland. — ^The problem, in the 

 solution of which consists the mathematical theory of heat, is the 

 following : — Having given the state of heating, or the variation 

 of that state from time to time, at one or more points of a homo- 

 geneous body of given form and dimensions, to find the perma- 

 nent or variable temperature at every other point. Thus a ring 

 is kept at a certain temperature at one point, and it is proposed to 

 discover : 1. What is the variation from time to time of the tem- 

 perature at every other point. 2. What is the ultimate tempera- 

 ture to which that at any given point approaches, as the time 

 during which the constant heating of one point has been kept up, 

 is increased. From this statement it will appear that the experi- 

 mental facts on which the theory must rest, are the answers to 

 the following questions. 1. According to what law does a heated 

 body lose its temperature to the air, or other medium or space, by 

 which it is surrounded ? 2. According to what law is the tem- 

 perature transmitted from point to point of a body ? On the cor- 

 rectness of the answers which may be assumed as given to these 

 questions, depends the applicability of the results obtained to the 

 state of things in nature. The Report then proceeded to show 

 what answers have been given to the above questions by different- 

 theorists, and to explain the evidence on which their truth was 

 supposed to be established. 



On the temperature of the Air in York Minster, by Prof. 

 PhiUips. It may be remarked that the vastness and loftiness of 

 the interior of York Minster renders the air within it, in a great 

 degree, free from violent local draughts, and yet subject to a con- 



Vol. xLii, No. 1.— Oct.-Dec. 1841. 21 



