W. J. Mc Gee—Secular Chimatal Changes. 439 
In computing the means the following coefficients were 
employed : 
Latitude. Coefficient. 
0° 1°00 
20 "658 
40 "357 
60 134 
Polar circle 074 
The mean annual temperatures are 70°8° and 66°1° sg eh a 
It thus appears that the mean temperature is 4°7° lower and 
the thermometrical range 20°5° greater over the land- aedenie 
than over the water-meridian; which ratio yields a coefficient 
of diminution of 0-23° for each degree of increase in range. 
For the present this ratio may be assumed to remain constant. 
When the solstices are at right angles to the apsides the 
seasons. The amount so received may be denominated the 
normal accession. When, however, es solstices coincide with 
the apsides that hemisphere whose winters occur in aphelion 
while its summers occur in perihelion receives a less than nor- 
mal amount of light and heat in winter, and a greater than 
normal amount in summer, owing to the variation in the earth’s 
distance from the sun at these seasons. Tf, then, terrestrial tem- 
perature is a function of solar accession, the annual thermome- 
trical range on the hemisphere so situated must be greater than 
the normal; while at the same time the thermometrical range 
must be diminished on the opposite hemisphere. Manifestly, 
too, any increase in the eccentricity of the terrestrial orbit must 
intensify this effect, since solar accession varies as the square of 
the solar distance 
In table IT the solar accession in winter and summer when 
the solstices and apsides coincide and the eccentricity of the 
terrestrial orbit is as at present (0°0168), is compared with the 
normal, values being expressed in degrees Fahrenheit. Table 
III exhibits like values for an eccentricity of 0°0747, such as 
occurred 850,000 years ago according to Croll’s calculation 
from LeVerrier’s formulz.* ite tables are ae lseall y depicted 
in the accompanying diagra 
These tables were porpuied as follows :—The relative solar 
“Climate and Time,” p. 319. Stockwell computes the maximum eccentri 
to a 00693888 (* ~ the Secular Variations of the oc sgpeF of the Orbits of pv 
oy Principal Planets,” Smithso owledge, No. 232 et gate 
; but his + maar was not accessible when the ae was prepared 
sigh diminution in normal accession accompanying increased eccentricity is an 
" 
