Pa E. Loomis— Results from an examination of the 
and this condition must be favorable to a rapid extension of 
the rain-area in front of a storm. When, at a given place in 
front of a storm center, a system of causes is in operation 
which is soon to result in a fall of rain, the ordinary change of 
temperature at evening must accelerate the commencement of 
the rainfall; that is, must extend the rain-area_more ra ier 
This extension of the rain-area in front of a storm does not 
perhaps necessarily imply an increase in the average rainfall 
for that part of the day; nevertheless, I have endeavored to 
determine whether there is a diurnal inequality in the fall 
of rain. For this purpose I first examined the observations 
reported to a been in good condition. In the iolowing 
table, column second shows the aggregate amount of rain at 
Philadelphia. for each hour of the day during these seven 
months. 
Rainfall at Philadelphia. 
Hour. Posy Average. Hour. rare Average. 
Midnight} 1°633 0-869 Noon 0-366 0914 
1am] 0°748 917 PPC <-1s3 861 
2 98 826 2 1488 1-036 
3 666 "636 3 0-869 1°152 
4 686 617 4 1727 1-265 
5 84 “13k 5 1°234 
6 949 “T16 6 1346 1-580 
7 671 133 7 1-2: 1:310 
8 588 822 8 27598 1°206 
9 171 802 Oot SG 1°165 
10 17133 “T41 10 “42 1-235 
ll 0°848 780 1l 17140 0°865 
As these numbers show considerable irregularities, I_ have 
taken the average of each successive five numbers in column 
second and set down the results in column third. ese 
resulting numbers show a pretty steady progress from a mini- 
mum at 3 A. M. to'a maximum about 6 P. M., and from thence 
a steady decline to the ott minimum. The poeeae is 
nearly 24 times the minimum, although the former is made too 
small, and the latter too oreat b. the mode of reduction 
employed. It seems probable, therefore, that the diurnal in- 
equality in the rainfall, as indicated by these observations, is @ 
law of the Philadelphia climate, and we may presume, there- 
fore, that it is a law for the immediate vicinity of Philadelphia. 
I next examined the observations made at the signal service 
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