S Professor Macaire on the 



days. Theodore rose at four o'clock in the morning to com- 

 mence the meteorological observations ; he went to bed at ten 

 in the evening, and his father sat up till midnight. Theodore 

 twice observed the meridian height of the sun in order to deter- 

 mine the latitude of their station, which he calculated to be 45° 

 49' 54". He measured a base of 1200 feet for trigonometrical 

 observations. He made observations on the density of the air 

 by means of the vibrations of the pendulum, observations 

 which he had an opportunity of repeating on Mont Rosa by a 

 more conclusive process. He found the means of rectifying 

 sulphuric ether, which he prepared and carried with him, and 

 he found this fluid so expansible, in consequence of the rarity 

 of the air, that he could succeed in distilling it only by making 

 an aperture in the luting, which united the receiver to the retort. 

 The ether entered into a state of ebullition in water heated to 23'^ 

 R. (83-7 F.) He carried on eudiometric experiments by means 

 of nitrous gas ; and, having previously determined the com- 

 position of the air of Geneva to be similar to that of the air of 

 Chamouny, he thought that that of the Col du Geant contained 

 somewhat less oxygen, 0-0125, than the two others. In the 

 air of the Col also he ascertained the presence of carbonic acid, 

 as in that of the plain. He found that iron dissolved with 

 effervescence in sulphuric acid, as in the plain ; while copper 

 would scarcely dissolve, which he attributed to the rarity of 

 the air. With these points he alone was occupied ; but he 

 assisted his father besides in all his observations on physics 

 and meteorology, with the electrometer, hygrometer, cyan- 

 ometer, on the evaporation of water and ether, on magnetism, 

 with the barometer, which they observed eighty-five times in 

 spite of the precautions it was necessary to adopt in order to 

 keep the stop- cock dry ; and finally with the thermometer, 

 which they observed every two hours, and which ascended and 

 descended nearly as on the plain. They estimated the dimi- 

 nution of the heat, in consequence of the height, at the hun- 

 dredth part of a degree of Reaumur's scale for every toise of 

 elevation. With regard to the barometer, it stood at the lowest 

 point at 8 o'clock in the morning, then ascended till 2 o'clock ; 

 descended from 2 to 4, and reascended the rest of the day. 

 At Chamouny and Geneva, on the contrary, 8 o'clock in the 



