33 



est and most severe storm of all occurred in February, 

 commencing on the 4th. Observations from 7 A. M. of 

 the 4th to the same hour on the 5th gave a range of 

 1.403. Other storms gave like results. On the 21st 

 of May thunder showers prevailed over an extended area ; 

 but none passed over the mountain or very near. The 

 barometer was depressed, owing more to the intensity of 

 magnetic force than other causes as the weather was fine 

 with us. The 22d was characteristic of the mountain. 

 It was warm, clear and calm in the morning, with a ter- 

 rific thunder storm at noon and wintry weather at night. 

 At 11 A.M. the temperature was 66 the highest during 

 the summer with one or two exceptions at 3 P.M. 26. 

 The barometric fluctuations were constantly going on 

 early in the morning, falling 1.124 from 8 A.M. to noon. 

 The oscillations of the barometer were in the same time 

 as the discharge of electricity at the telegraph table ; both 

 in the afternoon of the 21st and on the 22d. 



Humboldt has said, speaking of the horary variations 

 of the barometer, that "no atmospheric circumstances 

 neither rain, nor fair weather, nor wind, nor tempest 

 affects the perfect regularity of these oscillations under 

 the tropics ; but they subsist alike at all times and in all 

 seasons." 



We cannot say this of Mount Washington. On the 

 contrary, as the diurnal variation is governed by the rate 

 of the wind and amount of cloud, it is only in calm, 

 clear weather that it is at the usual hours, and, as it is sel- 

 dom clear or calm, it may be said that here it does not 

 conform to the general law. The tables of several sta- 

 tions in the New Hampshire Geological Report, compared 

 with Mount Washington, show that on the mountain, 

 there are times of high and low pressure which do not 

 extend to the lower stations. These seem to be confined 



ESSEX INST. BULLETIN. iv 5 



