114 Dr Barry's Ascent to the Summit of Mont Blanc. 



the slope of the north side forming an angle, estimated by De 

 Saussiire (in 1787) at 40^-50° ; that on the south 15°-20°. This 

 estimate, which applies to the covering of snow, may be consi- 

 dered as not materially different at the present time. 



I found the height of the barometer to be = 17,052 English 

 inches, the attached thermometer indicating 32° F., suspended, 

 and screened by the incasing wood from the sun's rays : a breeze 

 blowing from the south. 



De Saussure found the boiling point of water at the summit 

 of Mont Blanc to be 68°,993 R. (= 187°,234 F.) Naturally 

 wishing to repeat this interesting experiment, I had a fire light- 

 ed in a chauffer, provided for the purpose. With the aid of 

 bellows, our materials, wood and charcoal, were kindled with less 

 trouble than had been anticipated (Couttet assuring me that this 

 had never been done before). * In a culinary utensil of water, 

 in full ebullition, I immersed a thermometer, which I had pro- 

 cured at Chamonix (my own thermometer having been broken), 

 and carefully observed the height of the mercury when it ceased 

 to rise. I am sorry, however, that I am prevented from here 

 inserting the temperature indicated. The scale was found to be 

 loose, and the graduation very inaccurate, as since discovered on 

 comparing it with a standard. It did not bear the maker's 

 name. 



The report of a pistol, twice fired, was found very feeble. It 

 may be worth noticing, in connection with the subject of sound, 

 that when within a few hundred feet of the summit, in ascend- 

 ing, the snow being hard and its surface glossy, and some of the 

 guides considerably in advance, the creaking noise produced by 

 the points of their batons in the snow, as it reached me, could 

 be compared to nothing but the distant lowing of cattle. 



While on the summit, Couttet fetched me specimens from 

 the Rochers Meridionales, the highest rocks on its south side. 

 One of these, marked (A), is a granite ; two (B) are sienites, 

 consisting of a blackisL hornblende and white felspar, in inti- 

 mate aggregation ; the fourth (C) is hornblende, with veins of 



" 1 have since found, that De Saussure had a charcoal fire made on the 

 summit ; but finding it very difficult to support it, he used it only for the 

 purpose of melting snow. A spirit-lamp was employed by him for the boil- 

 ing of water. 



