442 W. J. McGee—Secular Climatal Changes. 
intensity at the various terrestrial latitudes has been calculated 
eech* and expressed in arbitrary units, each representing 
wy ofj the intensity under the equator at the time of the vernal 
equinox. ‘T’he mean for the whole earth, in sie same units, is 
66°73. Dove had previously, as a result of an elaborate series 
of observations, determined the actual mean temperature of the 
earth to be about 58° F. AasoRES to Herschel’s determina- 
tion of the temperature of space (which agrees pretty closely 
with that of Pouillet), or —239°, this temperature is 297° higher 
than that of stellar space. Each of Meech’s units is, therefore, 
so far as the whole earth is ee, equal to 4 45° F This 
coefficient has also been assumed to be constant; and the 
intensities, both normal and A ronane ss to the different 
degrees of eaves f have been reduced to degrees Fahren- 
heit by its The means were computed by the use of the 
following SCAMIGRS 
Latitude. Coefficient. 
0° 1°00 
10 826 
20 *658 
30 500 
40 "B57 
50 "234 
60 "134 
70 "060 
80 "015 
90 ‘001 
The increase in thermometrical range beyond normal in 
tables II and III is 21:0° and 93°7° respectively. Making 
use of the sonticiaet alvendy feces (0°23°), it appears 
that these values are equivalent to a diminution in mean tem- 
perature over the hemisphere whose winters occur in aphelion of 
4°83° and 21°55° respectively, and to a like increase in the tem- 
ones of the opposite hemisphere 
It may be added that aside from the specific relations pointed 
out, the alternate free summer precipitation and rapid winter 
congelation of seasons varying so widely in temperature would 
certainly facilitate the formation and conservation of glacier ice. 
In the foregoing pages two variable factors have bee 
sumed to be constant. These are the ratios (1) between increase 
in thermometrical range and diminution of mean temperature, 
The first of these ratios appears to augment rapidly with 
diminution of temperature, as may be seen a: a glance at 
* “On the Relative Intensity of oe — s Light and Heat,” vol. ix of Smith- 
sonian Contributions to Knowledge, 1 
