70 ON VENTILATING HOTHOUSES, AND GLAZING WITH SHEET GLASS. 
drains from grass fields on its eastern boundary, and the only outlet for the surplus water 
had long been discharged by a deep furrow which passed between two of the slopes toward 
the chalk-pit, but where it found no ingress, and consequently overflowed the lowest portion 
of land, and converted a very large extent of it into a complete bog. 
At length the occupiers eyes were opened, and a deep, broad drain was quickly 
opened, and led in a pretty straight line into the chalk-pit, where, as a natural consequence, 
a pond is formed, to the great advantage of the land, and nearly an acre of diseased swamp 
has been drained. Thus that element which was rendered a cause of great injury has 
been converted into a substantive good.^^ 
The phenomenon of the dark spots in newly moved soil may be explained, as we find 
it to be in the "Book of the Farm." When the surface of the ground is permeable to 
water, and rests on beds of different lengths, breadths, and depths, differing also in 
consistence, the water supplied by the heavens is interrupted in its descent by the retentive 
substratum, and there becomes accumulated in quantity and extent, according with the 
form and capacity of that substratum. Thus, where the upper soil is pervious, and the 
subsoil uniformly retentive, water accumulates on that subsoil, to the injury of plants 
growing on the surface soil, and numerous drains are required to permit it to pass away. On 
the contrary, where the soil and subsoil are both porous, the water can pass quickly through 
them, and no draining is required, because the subsoil constitutes and acts as a universal 
drain. In the latter instance, dark spottings will never remain visible, for the fresh moved 
soil will present an uniform tint, however rapidly or slowly the surface may be acted on by 
the power of the sun. 
Depth of tillage and pulverisation form another subject, which need not at this time be 
investigated. 
In this age of inquiry, when persons of science are not contented to observe mere facts, 
but are bent upon the discovery of causes, I have appealed to the Essay by Mr. Parkes, in 
which great stress is laid upon the chemical action of heat in converting water into vapour. 
The practical gardener, who perceives the importance of scientific research, ought to peruse 
those works which treat of draining, connected with geology. Pure mechanical knowledge 
of the construction of drains does not grasp a single idea of the chemical agency of 
sandstone, limestone, or any of the other rock formations upon which the labourable soils 
repose. Mr. Stephens, in his first edition, to which I am so much indebted, has paved 
the way for new discoveries. But his second edition is in rapid progress, and to it 1 hope 
we may hereafter most profitably refer. 
ON VENTILATING HOTHOUSES, AND GLAZING WITH SHEET GLASS. 
By Mr. R. Errington, F.H.S., Oulton Pwh, near Tarporley. 
No question has more agitated the horticultural portion of the public, in these later times, 
than that of the propriety of using sheet glass. For years the gardening world wandered 
on, content with a murky sort of atmosphere, produced by the unlucky conjunction of 
inferior glass, small panes, and unwieldy laps ; until at last the immense importance of 
light to vegetation being fully recognized, people began to question the old practices ; and 
the introduction of a much brighter glass took place — brighter, not from its innate clear- 
ness alone, but from its size also ; whereby the frequency of laps, common to the old 
practice — are obviated. 
It ought to have been easily foreseen that the ventilation question was closely wound up 
in this ; and that, as those aerating apertures were dispensed with, an equivalent ought to 
be provided. Indeed, if such were not the case, it would not be difficult to prove that, by the 
old system, houses were over-ventilated : this, however, I hold to be impossible, maugre 
* Scarcely three days elapsed after this paper went to press, ere this noble drain was entirely ruined, and filled up by 
the fearful hurricane and deluge that occurred on the Stitli February. Drainers ought never to leave their work half 
done : the water course at bottom should be secured by pipes, or other solid materials, without loss of time. 
