Chase.] 122 [May 5th, 1871 
ances the principal maxima occur in the spring of the year and the 
morning of the day, while the general evaporation is increasing, whereas, 
in the daily rains at Philadelphia, the principal maximum occurs in the 
afternoon, when evaporation is diminishing. I have, therefore, compared 
the midwinter ordinate of the auroral with the noon ordinate of the rain 
curve, and the midsummer auroral with the midnight hyetal ordinate. 
The auroral observations and the normal ordinates of the accompanying 
curves, are given in the following table. I presume no one will doubt 
that the condensation of vapor, which is represented by the rain curve, is 
occasioned by the simple operation of gravitation in blending currents of 
different temperatures, and I see no reason for postulating any different 
law for the development of electricity and magnetism in the aurora. 
Comparative Table of Auroras and Rainfalls. 
w k 4 © + a + ° 
ome ge eB.  oBigegeue one 
i ee | 5 asl so 8 5 x5 
Zo 2 ee =. © ae % = 
2 hh BG Bel B it 
88 0 9 100 12 103 
January ....82 90 aN Qi || July ee ees es oo 101 3 106 
94. 2 93 103 14 109 
February ...31 98 3 98 |} August.....384 105 15 108 
108 4 105 107 16 104 
March... Aes 107 5 110 ||September..43 106 ue 98 
109 6 118 103 18 92 
Api 2 c 44 109 7: 118. || October, «2.98... 100 19 87 
108 tele Pala, 95 20 85 
May isisch 3 86 =: 106 9 109 || November . .27 O1 21 87 
103 10 8105 89 22 90 
IMME ce ts Dis 10 11 102 |! December.. .30 87 2¢ 91 
