by waiting till another season we were sure of obtaining less unfavourable conditions of snow and ice upon the mountain.-We had enjoyed an exciting and adventurous day, and I myself was not sorry to have something still left to do, while we had the satisfaction of being the first to set foot on this, the most imposing and mightiest giant of the Alps-the inaccessible' Mont Cervin.-Vacation Tourists, 1860.

IV.

THERMOMETRIC STATION ON MONT

BLANC.

THE thermometers referred to at p. 17 were placed on Mont Blanc in 1859. I had proposed to the Royal Society some time previously to establish a series of stations between the top and bottom of the mountain, and the council of the society was kind enough to give me its countenance and aid in the undertaking. At Chamouni I had a number of wooden piles shod with iron. The one intended for the summit was twelve feet long and three inches square; the others, each ten feet long, were intended for five stations between the top of the mountain and the bottom of the Glacier de Bossons. Each post was furnished with a small cross-piece, to which a horizontal minimum thermometer might be attached. Six-and-twenty porters were found necessary to carry all the apparatus to the Grands Mulets, whence fourteen of them were immediately sent back. The other twelve, with one exception, reached the summit, whence six of them were sent

back. Six therefore remained. In addition to these we had three guides, Auguste Balmat being the principal one; these, with Dr. 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 transparency of the lower strata of the atmosphere to the solar heatrays. I therefore arranged a series of observations with the Abbé Veuillet, of Chamouni; he was to operate in the valley, while I observed at the top. Our instruments were of the same kind; in this 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 daybreak, I had a tent carried to the summit, where I proposed to spend the night. The tent was ten 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 we had no fire, and the adjacent snow was 15° Cent., or 27° Fahr., below the freezing point of water. We were all however indisposed. I was indeed very unwell when I quitted Chamouni; but had I faltered my party would have melted away. I had

ascent.

frequently cast off illness on previous occasions, and hoped to do so now. But in this I was unsuccessful; my illness was more deep-rooted than ordinary, and it augmented during the entire period of the Towards morning, however, I became stronger, while with some of my companions the reverse was the case. At daybreak the wind increased in force, and as the fine snow was perfectly dry, it was driven over us in clouds. Had no other obstacle existed, this alone would have been sufficient to render the observations on solar radiation impossible. We were therefore obliged to limit. ourselves to the principal object of the expedition—the erection of the post for the thermometers. It was sunk six feet in the snow, while the remaining six feet were exposed to the air. A minimum thermometer was screwed firmly on to the crosspiece 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 six, and the other at a depth of four feet below the surface-these being intended to give some information 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 ones 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 (though we did not know it) penetrated the mist, and was seen at Chamouni. Lecomte's experiments on the alleged influence of light and rarefaction in retarding combustion caused me to resolve on making a series of experiments on Mont Blanc. Dr. Frankland was kind enough to undertake their execution. Six candles 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 Chamouni. They were afterwards permitted to burn an hour below. Rejecting one candle, which gave a somewhat anomalous result, we found that the quantity consumed above 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