42 



to obtain the full account of the circumstances under which 

 we were working, than for a regular and systematic meteoro- 

 logical record. The tables explain themselves, giving in 

 separate columns the various necessary elements, viz. : Date, 

 time, temperature, barometer observed, barometer reduced to 

 the freezing point, wet and dry bulb thermometers, their 

 difference and the relative humidity derived from it, the 

 wind's direction and force, the cloudiness and the nature of 

 the clouds, with some remarks on the state of the weather. 



The storms which we encountered were without doubt the 

 result of the overheating of those large and elevated plateaus, 

 the inclined sides of which, as well as the mountain slopes, 

 expose a larger surface to the rays of the sun than would a 

 merely flat body. These circumstances would seem to help 

 the formation of strong ascending currents, which, having 

 once been started, furnish ample material for the midday 

 showers. These storms gradually extend their limits, as to 

 time, until the rainy season is complete. They seemed to be 

 similar to those of tropical regions, and this fact enabled us to 

 explain the presence of such large quantities of electricity in 

 the air. Once only, during our stay, did we observe two 

 different layers of clouds, one above the other, moving in 

 opposite directions. Their line of motion was almost due 

 N. E. and S. W., the upper one moving S. W. This was seen 

 from the cliff on which No. 9 is situated, and was watched 

 as a great curiosity, as one cloud was almost on a level 

 with us, and the other some distance above. We were now 

 and then favored with beautiful rainbows, on two occa- 

 sions seeing triple arcs, and a single one was the exception 

 rather than the rule. The temperature during the first part 

 of our stay was quite favorable to our work, being just cool 

 enough for the exercise of brisk walking during the day ; but 

 at night generally freezing the edges of the brook near our 

 camp, or any water left out in small vessels, thus making a 

 number of blankets very necessary articles for our comfort ; 

 and a blazing camp-fire of pine stumps not only a pleasure to 

 the eyes, but to the fingers also. Before the end of our stay 

 (our camp was at a height of 10,500 feet), we needed all 

 our heavy clothing and generally a fire all day as well as at 

 night. 



