46 W. Dennis on the Temperature of 
rature takes place: when the loss exceeds the gain a gradual 
reduction must of course result. It is by these two processes 
respectively that the high heat of summer and the severe cold 
of winter are produced. As it follows directly from the law of 
compensation just explained that the same amount of heat is re 
ceived froin the sun during each of the two winters (northern 
and southern) and also the same amount during each of the two 
summers, the question of the effects of the variations under con- 
sideration turns upon the influence which they shall appear to 
have upon that gradual elevation, and that gradual reduction of 
temperature from which, as just stated, the extremes of these 
two seasons result. It will enable us to estimate more correctly 
the extent and importance of these effvets to observe how pees 
are concentrated, so to speak, upon these two seasons. Thus 
sun is not quite 72 days longer north of the equator ae south 
of it in the tropical year, while it is 42 days, or more than 2 
of this whole difference, longer in the north or apogee dace 
than in the soath or perigee quadrant of the ecliptic: the north- 
ern summer is therefore 42 days longer than the southern and the 
northern winter shorter than the southern by the same amount. 
Again, the whole change in the sun’s apparent sonia 
which is the index of its change of distance, amounts to 32”, 
ut in the apogee quadrant it varies from its minimum (about 
July 1) and in the perig igee quadrant from its maximum (Jan. 1 
only about 5”: in fact its mean pisuiencaesee while in either of 
these arcs does not differ from the extreme limit belonging to 
that are but about 15. To this it may be added, as not with- 
out a bearing on the same point, that the controlling cause itself 
of the change of seasons has its influence in like manner con- 
centrated upon these quadrants ; for while the maximum deeli- 
nation of the sun is but 234° its mean declination while in these 
two arcs is about 203° or its mean distance from the tropics re 
spectively less than 3°. Let us now keep in view the following 
1. The sun is at its perigee at midwinter and at its apogee 4 
midsummer, using those terms with reference to the north ail 
isphere 
D ae on mae the same amount of heat while passing through 
het apogee quadrant of the ecliptic, (Summer, north—winter, 
ponthy's as white in the perigee quadrant, (winter, north—sum- 
mer, a but is 4% days longer in the former than in the 
lat 
3. "While i in these quadrants it varies but little in the one from 
its maximum, and in the soi —s its minimum m dista ance; and 
its pooaici is On an averag r the maximum in both. 
ae The high heat of seesisey 0d the severe cold of winter are 
the results of a graddal accumulation of heat in the earth’s sur 
