481 



scientific pursuit, but you also facilitate it in those who may be- 

 come at once your followers and your rivals. In the particular case 

 before us, you have introduced accuracy where even rough numeri- 

 cal data were almost wholly wanting. The importance of such fa- 

 ciHties in any branch of science can hardly be overrated, and I have 

 therefore the greatest satisfaction in being the channel of this award 

 of the Council of the Royal Society. 



Mr. Daniell, 



I have to request that you will take charge of this Copley Medal, 

 and transmit it to M. Jean Baptiste Dumas, for his late valuable re- 

 searches in Organic Chemistry, and more especially those contained 

 in a series of memoirs on chemical types and the doctrine of substi- 

 tution, and also for his elaborate investigations of the atomic weights 

 of carbon, oxygen, hydrogen, nitrogen, and other elements. In be- 

 stowing this Medal, as awarded by the Council of the Royal Society 

 for scientific labours so important, I may well feel the highest grati- 

 fication*. 



the total incident heat at least, and may be even much greater ; so that the 

 absolute intensity of the solar ray, or such as it has exterior to our at- 

 mosphere, would appear to have been considerably under-rated. 



" 2nd. The extinction of heat in a mechanically pure atmosphere has a 

 limit, and beyond which it might traverse any, at least a very great additional 

 thickness, without further loss. 



" These conclusions are, however, only so far results of direct observation 

 as that they are concluded from it by following out an empirical curve be- 

 yond its observed limits. Yet when we examine the amount of deviations 

 the curve itself exhibits within those limits, and take into consideration 

 the very simple apparent law of its curvature and course, it will be allowed 

 that the conclusions partake at least of a very high probability, amply suf-. 

 ficient to warrant further research. 



" Besides the simultaneous observations on the Faulhorn and at Brientz, 

 Mr. Forbes has stated in this paper the results of a great many other acti- 

 nometric da3's' work, which go to show — 1st, that the instrument really is 

 one which (its use being fully understood) gives highly consistent and de- 

 pendable results ; 2ndly, that its indications are in a most remarkable 

 manner, and instantaneously affected by changes in the opacity of the at- 

 mosphere ; 3rdly, that in a great number of comparisons between its 

 indications on the summit of the Faulhorn with those simultaneously, or 

 nearly so, at a variety of lower stations, there occurs not one in which the 

 joss of heat between the stations is not a very large, distinct and easily 

 measurable quantity. 



" Mr. Forbes says nothing in this paper of the qualities as distinct 

 from the quantities and chromatic properties or indices of transmissibility 

 of the heat stopped in the upper regions of the air. But independent of 

 any considerations of this nature (which however may materially affect 

 the relations of vegetation to altitude in mountainous districts), I am dis- 

 posed to regard this paper as marking a considerable epoch in that depart- 

 ment of meteorology which relates to the introduction and distribution of 

 heat among the strata of our atmosphere, and as likely to be the fore- 

 runner of very extensive and elaborate researches in further prosecution of 

 the subject." 



* After the classification of organic substances under compound radicals, 

 no feature in the recent progress of chemistry is more remarkable than the 



