EXTRACTS -NATURAL HISTORY. 
327 
If the wind be westerly, a rainbow' in the morning indicates rain. The, baro¬ 
meter will then certainly descend, and very often the thermometer will be higher 
than the usual temperature of the season. But with the wind in the same quar¬ 
ter, especially when the western clouds have a bright tinge of red, a rainbow in 
the evening, towards sunset, is almost a sure presage of fine weather the follow¬ 
ing day. 
When it rains early in the day, with an easterly wind, the rain almost always 
continues until towards noon, but it is rather misty or drizzling rain than heavy 
showers. If it do not then clear up, the rain will not entirely cease before sunset. 
The wind following the sun in his diurnal course with a gentle breeze is a pre¬ 
sage of fine, and generally of settled weather. But if it backs from the west to¬ 
wards the south, rain may be expected. The barometer being concave, if the 
highest hills in the neighbourhood, in the morning, be cloud-capt, and remain 
so till afternoon, rain may be expected. But if the morning mist, on the summit 
of the hills, gradually disappears towards noon, fair weather will follow. Those 
who reside where there are no high hills in sight, may judge of the weather by 
the smoke of the chimnies. If it spread abroad, and scarcely rise above the 
house, rain may be expected in the course of the day. When it immediately 
descends below the roof of the house, rain is almost certain; but when the air is 
in a condensed state, the smoke will rise rapidly, and perpendicularly, if it be 
not immediately dispersed by the wind. It is sometimes unadvisedly said, that 
the air is heavy, and drives down the smoke, but the fact is precisely otherwise; 
for when the atmosphere is most condensed it immediately absorbs the smoke, 
as well as all other vapours and exhalations. Hence a condensed state of the 
atmosphere, which raises the barometer* produces fair weather, and the contrary 
high wind, and rain, or both. 
Notes on Mildew from a Lecture delivered by Professor Lindley, April 24, 
at the Horticultural Society’s Rooms, Regent-Street, London. One of the most 
important errors existing respecting Mildew, is the belief so common amongst 
gardeners and agriculturalists, that one kind of mildew will infect several kinds 
of plants. This can never be the case; for each tribe of plants has a mildew 
peculiar to itself, which cannot, under any circumstances affect plants of a dif¬ 
ferent kind. Mildew is nothing more than different kinds of fungi, or parasites, 
attacking different kinds of plants, varying in appearance and species according 
to the nature of the plants attacked. It is the greatest enemy to the agricultu¬ 
rist, but the gardener suffers severely from it. 
These fungi are divided into three classes:—1st. Those which grow, or rather 
lie on the surface of leaves, and which perhaps do not derive any nutriment from 
the plant. 2. Those which are formed in the interior of the stem or leaf, and 
protrude themselves from it when ripe. 3. Those which Only attack the roots. 
All are extremely simple in their organization, and very minute in their forms ; 
they seldom appear but in the autumn, except in forcing-houses. 
The first class, or mildew composed of those fungi that live on the surface of 
the leaves, injure a plant by preventing its respiration, though they do not ap¬ 
pear to draw any nourishment from it. One of the most common of the fungi 
which attack the common cabbage is the Cylindrosporium concentricum, (Fig. 
41,) having the appearance of small white patches, or specks of frosty in¬ 
crustation, which when magnified are found to consist of a number of small cy¬ 
linders, lying end to end or across each other. These are filled with seed and 
