TRANSACTIONS OF THE SECTIONS. 57 



Frankland and myself, made up eleven persons in all. Though the main object of 

 the Expedition was to plant the posts and fix the thermometers, I was very anxious 

 to make some observations on the diathermancy of the lower strata of the atmosphere. 

 I therefore arranged a series of observations with the Abbe Vueillet, of Chamouni ; 

 he was to operate in the valley, while I observed at the summit. Our instruments 

 were of the same kind ; and in tbis way I hoped to determine the influence of the 

 stratum of air interposed between the top and bottom of the mountain upon the 

 solar radiation. Wishing to commence the observations at an early hour in the 

 morning, I had a tent carried to the summit. It was 10 feet in diameter, and into 

 it the whole eleven of us were packed. The north wind blew rather fiercely over the 

 summit ; but we dropped down a few yards to leeward, and thus found shelter. 

 Throughout the night we did not suffer at all from cold, though the adjacent snow was 

 15° Centigrade, or 27° Fahr. below the freezing-point of water. We were all, however, 

 indisposed. I was, indeed, unwell when I quitted Chamouni ; but I fully expected 

 to be able to cast off the indisposition during the ascent : in this, however, I was un- 

 successful ; my illness augmented during the entire period of the ascent. The wind 

 increased in force towards morning ; and as the fine snow was perfectly dry, it was 

 driven upon us in clouds. Had no other obstacle existed, this alone would have been 

 sufficient to render the observations on solar radiation impossible. We were there- 

 fore obliged to limit ourselves to the principal object of the expedition — the erection 

 of the post for the thermometers. It wa3 sunk 6 feet in the snow, while the re- 

 maining 6 feet were exposed to the air. A minimum thermometer was screwed 

 firmly on to the cross-piece of the post; a maximum thermometer was screwed on 

 beneath this, and under this again a wet and dry bulb thermometer. Two minimum 

 thermometers were also placed in the snow ; one at a depth of 6", and the other at 

 a depth of 4 feet below the surface ; these being intended to give us some infor- 

 mation as to the depth to which the winter cold penetrates. At each of the other 

 stations we placed a minimum thermometer in the ice or snow, and a maximum and 

 a minimum in the air. The stations were as follows : — the summit, the Corridor, 

 the Grand Plateau, the glacier near the Grands Mulets, and two additional between 

 the Grands Mulets and the end of the Glacier de Bossons. We took up some 

 rockets, to see whether the ascensional power or the combustion was affected by the 

 rarity of the air. During the night, however, we were enveloped in a dense mist, 

 which defeated our purpose. One rocket was sent up, which appeared to penetrate 

 the mist, rising probably above it ; its sparks were seen at Chamouni. Dr. Frank- 

 land was also kind enough to undertake some experiments on combustion : six can- 

 dles were chosen at Chamouni, and carefully weighed. All of them were permitted 

 to burn for one hour at the top ; and were again weighed when we returned to Cha- 

 mouni. They were afterwards permitted to burn an hour below. Rejecting one 

 candle, which gave a somewhat anomalous result, we found that the quantity con- 

 sumed at the top was, within the limits of error, the same as that consumed at the 

 bottom. This result surprised us all the more, inasmuch as the light of the candles 

 appeared to be much feebler at the top than at the bottom of the mountain. The 

 explosion of a pistol was sensibly weaker at the top than at a low level. The short- 

 ness of the sound was remarkable ; but it bore no resemblance to the sound of a 

 cracker, to which, in acoustic treatises, it is usually compared. It resembled more 

 the sound produced by the expulsion of a cork fr m a champaene-bottle, but it was 

 much louder. The sunrise from the summit exceeded in magnificence anything that 

 I had previously seen. The snows on one side of the mountain were of a pure blue, 

 being illuminated by the reflected light of the sky ; the summit and the sunward face 

 of the mountain, on the contrary, were red, from the transmitted light ; and the con- 

 trast of both was finer than I can describe. I may add, in conclusion, that the lowest 

 temperature at the summit of the Jardin during last winter was 21° Cent, below zero. 

 We vainly endeavoured to find a thermometer which had been placed upon the sum- 

 mit of Mont Blanc last year. 



