HEATING HOT-HOUSES BY HOT-WATER. 
125 
ARTICLE III. 
UPON THE APPLICATION OF HOT-WATER IN HEATING HOT HOUSES. 
BY MR. THOMAS TREDGOLD. 
Extracted from his Paper.—Read before the London Horticultural Society, August 5th, 1828, 
and inserted in their “Transactions,” Vol. 7, page 568. 
The power of imitating other climes and other seasons than those 
which nature affords us, is known and valued as it ought to be; yet 
it remains difficult even to imagine the extent to which this power 
may be applied; in this age it produces luxuries of which few can 
enjoy more than the commonest species; but in the next—nay, 
even in our own, there is a reasonable expectation of a considerable 
addition to the quantity and quality of those artificial productions, 
as well as to the best sources of pleasure and information they afford 
to the admirers and students of nature. 
The vehicle employed to convey and distribute heat in the new 
process* is water, for it has been found that in an arrangement of 
vessels connected by pipes, the whole of the water these vessels and 
pipes contain, may be heated by applying heat to one of the vessels; 
and that in this manner—a great extent of heating surface, and a 
large body of hot-water to supply it, may be distributed so as to 
maintain an elevated and regular temperature in a house for plants, 
or indeed in any other place requiring heat. 
The obvious advantages of this method are, 1st. the mild and 
equal temperature it produces; for the hot surface cannot be hotter 
than boiling-water: 2nd. the power of heating such a body of water 
as will preserve the temperature of the house many hours without 
attention; and, 3rd. the freedom from smoke or other effluvia of 
smoke flues. In houses appropriated to plants, these advantages are 
most important. 
In order to develope the principles on which a hot-water appara¬ 
tus act?, we may select the simple case of two vessels placed on an 
horizontal plane, with two pipes to connect them ; the vessels being 
open at the top, and the one pipe connecting the lower parts of the 
vessels, and the other their upper parts. 
If the vessels and pipes be filled with water, (fig. 14) and heat be 
applied to vessel A, the effect of heat will expand the water in the 
vessel A; and its surface will, in consequence, rise to a higher level 
a, a; the former general level surface being b, b. 
* Alluding to the first discovery of the System, by Mr. W. Atkinson, and 
published in the Hort. Trans. Vol. 7, page 203. 
