1867.] Adinometi'ical Observations among the Alps. 321 



other ; and tliat he, thus judged^ evidently takes his place amongst the 

 members of the suborder Anthropoidea. 



A list of the principal osteological variations presented by the several 

 groups and genera of the order, before unmentioned, was then given ; and 

 the author concluded by stating what he believed to be the degrees of affi- 

 nity existing between the various forms, as far as could be ascertained from 

 the consideration of the appendicular skeleton exclusively. 



January 17, 1867. 



WILLIAM SPOTTISWOODE, Esq., Vice-President, in the Chair. 



The following communications were read : — 



I. " Actinometrical Observations among the Alps, with the Descrip- 

 tion of a new Actinometer.^' By the Rev. George C. Hodgkin- 

 soN. In a Letter to Professor Stokes, Sec. R.S. Communicated 

 by Professor Stokes. Received December 2, 1866. 



Sir,— I have the honour to forward you an account of some actinome- 

 trical observations made last summer on the summit of Mont Blanc and at 

 Chamonix, and at the same time to thank the Committee of the Royal 

 Society for the grant which they were so good as to vote me for that object. 



I reached Chamonix on the 7th of July, in bad weather, which had been 

 prevailing for some time, but which ushered in a fine week very opportunely 

 for my work. After allowing a few days for the weather to settle and for 

 the snow to consolidate, I left Chamonix in the afternoon of Friday the 13th 

 for the Grands Mulcts, having previously arranged for a corresponding 

 series of observations being taken the next morning in the valley. Leav- 

 ing the Grands Mulcts at about 21a.m. on the 14th, I reached the summit 

 of Mont Blanc about 8 a.m., and proceeded at once to work. 



I had brought with me from England two of Newman's mountain-baro- 

 meters, a thermobarometer of Casella, six small thermometers graduated on 

 the stem (three for the dry-, and three for the wet-bulb observations), 

 three of the tubes described in Appendix (A), with two of the actinometers 

 in each. I carried besides an aneroid by Cooke, which proved to be of 

 excellent quality. The third set of apparatus was taken in some faint hope 

 that I might be able to arrange for a third set of simultaneous readings at 

 the Grands Mulcts. In this I was disappointed. Notwithstanding the 

 greatest care had been taken, one of the barometers was found on the Bre- 

 vent on the 9th to be deranged, and one of the actinometers to be broken ; 

 and on the 12th a second actinometer was broken at Chamonix by an acci- 

 dent. I thought it best to leave the remaining barometer for the valley 

 observations, and to depend upon the thermobarometer, as being more por- 

 table and less Uable to fracture, for the readings on the summit. I was 

 eventually obliged to rest satisfied with a single observation of this ; and 

 the downward range of the small thermometer unfortunately proved too 



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