210 Royal Society. Anniversary Proceedings, 1843. 



researches, as one of the fruits of his arduous and meritorious la- 

 bours amid the eternal ice and snows of the loftiest region of Europe. 

 Mr. Forbes is now fairly enlisted in that enterprising scientific band 

 which looks up to De Saussure as its leader. His researches into 

 the law of extinction of the sun's rays is but a portion of the valu- 

 able results that he has obtained among the mountain solitudes, 

 where, though vegetation scarcely exists, and animal life is equally 

 rare, the eternal glacier itself is ever pursuing its gradual and silent 

 course : — silent, till it is interrogated by a philosopher endowed with 

 the energy and perseverance of a De Saussure in the eighteenth, or 

 a Forbes in the nineteenth century. 

 Mr. Wheatstone, 

 I now present you with this Medal, one of those entrusted to the 

 President and Council of the Royal Society by Her Most Gracious 

 Majesty, for your paper entitled " An account of several new Instru- 

 ments and Processes for determining the Constants of a Voltaic Cir- 

 cuit*." This is not the first time that I have had the pleasing task 

 of acknowledging, on the part of the Royal Society, the great inge- 

 nuity as well as knowledge that you bring to the increase of science. 

 You not only add to our store of knowledge, but you give to others 

 the means of doing so too. You not only set the example of 

 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- 

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



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 days' 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 

 loss 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." 



[* For an abstract of this paper see Phil. Mag. S. 3. vol. xxiii. p. 381.] 



[ a For an account of the actinometer see Phil. Mag. S. 3. vol. xv. p. 307.] 



