IQg MA UN A LOA. 



On the 10th of January, we had snow again. The temperature rose 

 to 32° : the snow melted fast, causing excessive dampness within and 

 without, while other discomforts that may be imagined prevailed. 

 Towards night, it cleared off, the wind hauling round to the west- 

 ward. The temperature fell quickly to 16°, when for a few hours it 

 blew a perfect hurricane. I thought the pendulum-house in great 

 danger : it rocked to and fro, appearing at times to be lifted from the 

 ground, and several of its staples were drawn out. Not a person in 

 the camp could sleep until towards daylight, when the gale began to 

 abate. 



These gales reminded me strongly of those we experienced among 

 the ice on the Antarctic cruise. I regretted I had no anemometer, to 

 ascertain the direction, changes, and force of the wind. It is remark- 

 able that these severe gales all occurred during the night, beginning 

 in the evening and continuing until the next morning. I attempted 

 to ascertain the velocity of the clouds by the rate of progress of their 

 shadow across the crater, marking the time of the passage ; and the 

 greatest velocity in many trials of those from the southwest, was 

 about forty-seven miles an hour. It was, however, observed, in these 

 experiments, that the swiftness of the clouds seemed to increase in 

 passing over the apex of the cone or crater. Whether this was the 

 effect of being able to compare their movements more nearly with 

 fixed objects, I am not prepared to say ; but I am inclined to believe 

 that in some cases, as they touched the mountain-side, they were 

 forced upwards and over the summit, with a much greater velocity 

 for the first half of the crater than the last. The shortness of the 

 time that elapsed in passing the diameter of the crater, little more 

 than a mile, precludes the supposition that they had changed their 

 form sufficiently to alter the figure of their shadow. The wind was 

 blowing what would be termed a strong gale, when the experiments 

 were made. 



On the 11th, having the eprouvette mortar with me, I tried some 

 experiments on the velocity of sound, comparing it with our measured 

 bases and the sides of the triangles : these gave results as satisfactory 

 as those usually obtained below. The great diflFerence was in the 

 sound itself: the report of the gun producing a kind of hissing noise. 

 The eprouvette was of iron, and was fired with a plug driven into it 

 very tightly after it was loaded. When fired near the level of the sea, 

 it was necessary to close the ears when standing within twenty feet 



