144 THE LIFE OF JAMES V. FORBES. [CHAP. 



are not equally polarized contrary to the opinion of 

 Mr. Melloni and consequently it is possible, as I have 

 suggested at page 9 of that paper, that there are normal 

 vibrations combined with transverse, and more abun- 

 dantly, as the temperature of the source is lower. . . . 

 I see no difficulty in constructing graphically the 

 ellipse in the case of heat. AVould not this be the most 

 satisfactory way ? Can you suggest any mode of deter- 

 mining the length of the wave in the case of heat ? In 

 depolarization we only get the ratio of ^-? . I have 

 sometimes thought of applying the ellipticity of the ray 

 in the case of Fresnel's rhomb, when the angles do not 

 give circular polarization, to this purpose. . . / 



To PROF. PHILLIPS, York. 



< EDINBURGH, December 11*7*, 1839. 



1 . . . I believe in my conscience that I am better 

 employed now than in writing reports. I have fields, 

 not of untrodden snow, but of untrodden heat, before 

 me, all promising a rich harvest. Cauchy has just set 

 me a task to which I must buckle myself. . . . ' 



To PROFESSOR POWELL. 



'EDINBURGH, December '27th, 1839. 



* ... I own that I should be very glad to see a good 

 synopsis of what has been done during the last eight 

 years, well aware that, so far as my own contributions 

 are concerned, they were published in a form repulsive to 

 the generality of readers, and even to many men of science 

 who would willingly glean from your critical pages how 

 much has been established, and on what kind of evidence, 

 without troubling themselves about details. . . . 



'I hope that you will not treat Melloni's papers so slightly 

 as you propose. His earlier ones are full of interesting 

 and original experiments. So far as I am concerned, 1 

 have nothing to wish but that everything Melloni Jias 

 done should be fully and accurately known, for by a rare 

 good fortune there is not a single debate in point <>f 

 priority between us, and every experiment we have in 



