304 
HARRINGTON. 
vated plains become the warmer compared with air at the 
same level over the ocean. Late in the afternoon this dif¬ 
ference reaches a maximum and may be very great, and a 
strong inland northerly current is in progress. This con¬ 
dition lasts w T ell into the night and again begins the next 
morning immediately after sunrise. Whether the cooling 
to the minimum at sunrise is enough to greatly retard this 
northward movement, or even to bring it to rest and per¬ 
haps start a return current, is a matter for observation to 
decide. The decision appears to be in the negative, which 
is in accordance with the facts in other monsoon regions. 
Moreover, if a. return even started during the night the 
phenomenon would become a simple land and sea breeze, 
and the theory of such a breeze is absurd when applied over 
a territory part of which is from five hundred to one thou¬ 
sand miles from the sea. 
Charts representing isotherms reduced to sea-level (when 
this reduction is correctly made) may be safely used in 
the study of monsoonal winds, for the contrast of tem¬ 
peratures at any level, to which the motion is due, is the 
contrast between the temperature of the plain and that of 
air at the same sea level in adjacent lower regions. As the 
temperature decreases more rapidly in a vertical direction 
in free air than on the slopes of mountains, the charts of 
isotherms reduced to sea-level must show smaller contrasts 
of temperature than are actually existent for producing 
monsoons. Armed with this fact, Dr. Hann’s excellent 
chart of July isotherms for the globe may be examined.* 
It is here found that the reduced temperature of Texas, Okla¬ 
homa, Colorado, and the western parts of Indian Territory 
and Kansas have about the same mean temperature as the 
western Gulf and Yucatan. As the elevation of the States 
is greater, a steady monsoon from the south in July should 
result, except in so far as it is interrupted by cyclonic and 
anti-cyclonic action. The same thing would in its degree 
be true for the neighboring months. 
*Hann (Julius). Juli-Isothermen. [In Berghaus {dr. TI.) Physika- 
lischer atlas, etc., fol. Gotlia, J. Perthes, 1886. Map no. 29.] 
