. 289 
Notes and Observations on the Botany, Weather, &c., of the United 
States, made during a tour in that country in 1846 and 1847. By 
Wa. ARNOLD BnourrELD», M.D., F.L.S., &e. 
(Continued from vol. i. p. 274.) 
The very moderate heat of summer, compared with the dispropor- 
tionate cold óf winter, at places situated under the higher latitudes 
and in the centre of large tracts of land, remote from oceanic influence, 
is easily accounted for. During winter in these regions very little fall 
of any kind takes place after the snows at its beginning have descended 
and covered the face of the country; the sky for the remainder of the 
season is for the most part clear, and terrestrial radiation goes on with 
but little interruption from clouds or vapour for several months 
together, generating an extremely low temperature both of the earth 
and air, augmented by the intense cold brought by the north and 
north-east winds which then prevail. In the spring, the sun’s heat is 
expended in freeing the earth from its covering of snow, and in 
thawing the superficial frozen stratum beneath it, and, from the quantity 
of caloric thus absorbed or rendered latent in the process, it is long ere 
the temperature of the soil can begin to rise above the freezing point, 
and heat, in its turn, the superincumbent atmosphere. During the few 
summer and autumn months that succeed the long and dreary winter, 
the greater part of the annual fall of rain takes place ;* clouds more 
frequently intereept the sun’s rays, and with the evaporation prevent 
the heat from becoming for any length of time excessive. Severe night 
frosts early in August, and which often blight the hopes of the hus- 
bandman, contribute still more to reduce the mean heat of the summers 
to an equality with those of western Europe. Such deeply inland 
regions, like the deserts of Africa and Arabia, seem fitted only for the 
pastoral life of barbarous and nomadic tribes, such as at present 
wander over them, and would require all the appliances and resources 
of modern science and civilization to counteract the effect of climate 
ere they could be rendered tolerable as the permanent home of refined 
and enterprising’ communities. The mitigated temperature of coun- 
tries within the range of oceanic influence has ever shown itself one of 
* In the heart of Siberiait is stated to rain four times more frequently in summer 
than in winter. 
VOL. II. =P 
