44 
THE FLORIST’S JOURNAL. 
moistness on the shaded sides of ditches, showing diminished tension and 
evaporative power in the atmosphere. 
This state of things continued for several days, the cirri forming during 
the day, and clearing off during the night,—only they gradually formed lower 
and lower in the air, and at last, passed into light cirro-cumuli. The first 
rain was a gentle trickling, hut it was soon followed by a pretty heavy shower; 
and there were some violent showers, with hail in some situations, but not in 
such quantity as to do much damage; and though there was some thunder, 
there was not much. 
These rains gave a general washing to the vegetation ; but they were not 
followed by that genial warmth and rapidity of growth which usually follow 
May showers, and not unfrequently April ones. On the contrary, the wind, 
at least in the vicinity of the metropolis, remained in the north-east quadrant 
of the horizon ; and, although it had none of the characters of a blighting wind, it 
was hard and cold ; and vegetation did not make much more progress under its 
influence than it had done under that of the dry weather which preceded. Seeds 
which had not previously been moistened, sprung up, but there was no seasonal 
epoch of any marked character. Indeed, up to the very moment at which 
we write, the cold which has followed the showers has been less favourable to 
vegetation than the drought was ; and it is not a little remarkable, or at all 
events out of the general course, that rain, which in the time of its coming 
was what we would call so seasonable, should have had so little beneficial 
influence upon vegetation. 
But though unusual, the cause of this is easily explained ; for the general 
saturation of the earth with moisture explains the whole. Moist earth is a very 
bad conductor of heat, not only on account of that which is absorbed in the 
process of evaporation, but also in the passage through its own substance. 
Thus, during the day, the evaporation at the surface, in a great measure neu¬ 
tralizes the influence of the sun, while the humidity prevents that influence 
from penetrating the mass of the earth, which it does when that mass is dry, 
and then radiates, and so warms the atmosphere during the night. Weakened 
by the surface evaporation, the sunbeams of May, 1840, have been feeble and 
comparatively effectless; and deprived of the usual radiation of heat from the 
earth, the nights have been chilly,—and they may continue so much further 
into the season. That this will affect many flowers, and, among others, 
the Dahlia, is very obvious ; but the effect there will be less severe than upon 
those culinary vegetables which work much under ground; and the market 
gardeners are now complaining as much of the scanty crop of asparagus, as 
they did of that of radishes during the drought. 
To such as know or care no more about the weather than to notice it as it 
passes, and grumble at it for not being exactly what they wish, these remarks 
may seem tedious ; but the subject is one of deep interest to every one who culti¬ 
vates, or who makes a profit, or lives on what is cultivated; and the present 
season gives scope for a little insight into the true philosophy of the matter. 
Heat and moisture are the two grand stimuli to vegetation; and there is a 
certain balance of these, discoverable only by observation, which is best suited 
for each different climate, soil, situation, and plant. W here humidity is in 
excess, there is a tendency to uniformity of temperature, for the same reason 
