414 Proceedings of the Royal Society 
equator by the sun northward and southward, the different degrees 
in which the sea and land are heated by the sun’s rays, the effect 
of cloud in interrupting the h'eating action of the sun, and the 
influence of rain in cooling the air by the evaporation of its drops 
in descending towards the earth ; and he argues that we might 
explain all the phenomena of the winds, could we thoroughly 
appreciate in each instance under investigation the interference and 
relative energy of these and other subsidiary disturbing forces. He 
then illustrates these principles of inquiry by reference to our East 
winds in spring, and our West winds in summer and autumn. For 
the sake of brevity, I shall confine myself to the former topic, which 
is investigated with Hutton’s characteristic force and simplicity. 
In spring, says he, easterly winds prevail here, because the cold 
wintry air of the polar regions is drawn southward over the warmer 
continent of Europe and westward by the warmth of the German 
Ocean. For some time after it begins to blow in March and April 
it occasions in us a cold, uncomfortable feeling, because it is 
thermometrically cold, and also unduly dry. Its lowness of tem- 
perature, compared with the west wind, which occasionally inter- 
rupts it for a short period at this season, no one can dispute ; and 
Hutton had frequently remarked a thermometric difference of 
10° F. in favour of the interpolated west wind. The cold 
feeling thus occasioned is aggravated, he says, by the warmth 
created by the sun’s rays in sheltered places ; but, in particular, it 
is increased by the withering dryness of the wind, — for the common 
notion that an east wind is a damp wind is quite a mistake. 
During a long period of the spring it is a dry, parching wind, on 
that account alike disagreeable to the human race and blighting to 
vegetation. He tells us quaintly that he “never had a hygrometer;” 
but he improvised one, being nothing else than a somewhat rude 
wet-bulb thermometer, such as is now in constant use in a more 
perfect form ; and he tells us that in the east winds of early 
spring he sometimes found a difference of 10° F. between the 
wet and dry thermometers, while he never could observe a dif- 
ference of more than 4° F. in the driest days of summer. In the 
month of May, however, a change takes place in the character of 
the east wind. Still dominant, it encounters in its passage across 
the German Ocean a more and more powerful sun, which both 
