626 
KANSAS CITY REVIEW OF SCIENCE. 
As the atmosphere is a very poor conductor of heat the change at any station 
is solely the result of bodily movement of air from one place to another. Thus, 
if the temperature of a place 400 miles northwest of us is twenty degrees lower 
than it^^^is here and the wind is twenty miles an hour from the northwest, it will 
take twenty|hours for the temperature to fall those twenty degrees; and suppos- 
ing the wind to blow only ten hours at the rate mentioned, the temperature will 
fall only to that point which a station half of the distance northwest had at the 
time it started. 
This, stripped of all interfering circumstances, is the philosophy of areas of 
heat and cold. These interfering circumstances are, however, so numerous as 
to make the application of any abstract rule impossible, without many reserva- 
tions. 
It is not always true that a southerly wind is warmer than a northerly one. 
Very much depends upon the country over which the wind has passed. There 
may be fields of snow to the south and none to the north. There may be open 
bodies of water, forests, or even the modifying influence of large cities. Then, 
too, the wind we get from the south may not have come from a point very far 
south, but only deflected from a northerly direction. " The cold end of a south 
wind " is a proverb famiHar to all. 
But without entering into too many qualifying details, we may for the present 
take the following table of actinometry as approximately representing the differ- 
ence in temperature for every ten degrees from the equator to the pole in the 
northern hemisphere ; it shows the actual temperature due to the reception of 
heat from the sun : 
Latitude .... .... 

38 
48 
10 
59 
36 
48 
2C 
To 
32 
30 
63 
28 
"46 
40 
~66 
24 
45 
50 
67 
22 
44 
60 
68 
18 
43 
70 
66 
U 
40 
80 
T^ 
5 
35 
90 
Summer 
Winter 
Mean 
62 

31 
Taking latitude 40 (nearly that of Erie) we will have, in winter, a lower 
temperature of about 1° for every 200 miles we travel north and an increase of 
about 1° for every 200 miles we travel south. If, therefore, the temperature falls 
very low in the northwest at a place that is on a parallel 600 or 800 miles north, 
we do not expect as low a temperature here, but one which shall be from 5° to 
10° higher, as belonging to a lower latitude. And this again is modified by local 
conditions and the actual starting point of the wind which brings" with it the 
temperature experienced. The wind would have to blow all day at forty miles 
an hour to bring us the actual low temperature of stations a thousand miles 
northwest of us. Usually forty-eight hours at half that velocity is an exceptional 
occurrence. 
Similarly, if it should blow from the sonth with like continuance, we should 
have tropical weather as a result. 
So much depends upon the mean direction of the wind that the usual tracks 
of low barometer can never be omitted from our calculations. At Erie about 
