82 APPLICATION OF HEAT. 
therewith, all of which are very injurious to the gardener whose avocations confine 
him for hours in a large vinery or pine stove, saturated with water and vapour. 
Persons are in the habit of asserting that under certain circumstances " the air is 
burnt:" the expression is erroneous, though the effect produced would appear to 
sanction the fact. Thus, an "Arnott's stove" causes a disagreeable heat on the 
surface of the skin, rendering the face hot, while the feet become painfully cold ! 
The theory is simply this : the iron of the stove, heated by internal fire, attracts 
oxygen from the air, and leaves a predominance of the deleterious azote or nitrogen, 
a gas perfectly unfitted for respiration, and which disturbs the vital pulmonary 
functions. Plants have systems of breathing and transpiratory pores ; hence they 
sink under the influence of a dry poisoned atmosphere, and their vital functions 
become deranged. Watery vapour counteracts the effects of heated brick-surfaces, 
and of iron-cased stoves ; but its agency is not complete ; therefore we are called 
upon to search for melioration in the heating machinery of forcing-houses. 
The first and most important change (for improvement it can scarcely be consi- 
dered) was effected by the introduction of steam, of which a notable example was 
furnished by the late Mr. Loudon in his Encyclopaedia of Gardening, edition of 
1826, pp. 326 — 328, particularly at par. No. 1669. Keference is made to the 
garden, mansion, and farm-yard of Edward Gray, Esq., of Harringay-house, Hornsey, 
near London, "where ten large hothouses, and the largest of them 550 feet from 
the boiler, have been heated in a masterly manner by Messrs. Bailey." 
A plan is given of the work in p. 327. The houses thus heated comprised two 
graperies, two pineries, a peach-house, a strawberry pit, plant-stove, grapery, green- 
house, conservatory, a mushroom-house, in all 50,000 cubic feet of air, and hi addi- 
tion, it supplied a steam apparatus in the farm-yard. 
Among tradesmen and general gardeners, we believe that Messrs. Loddiges, of 
Hackney, were the first to adopt heating by steam in the large way ; but it was 
found there, and in every other situation, that, although the heat distributed by 
steam is nearly equal and certain, and, as Loudon observed, so regular as " never to 
heat the tubes, even close to the boiler, above 212 degrees, it will heat them to the 
same degree, or nearly so, at the distance of 1,000, 2,000, or an indefinite number 
of feet." Yet it cannot act at all unless the water which furnishes the steam be 
always kept actively boiling. This, then, was found the chief vice of the system, 
and thus, by accident, a whole range of buildings might be brought into danger by 
the sudden privation of its heating medium. Steam, therefore, failed, and was 
succeeded by the introduction of hot water: but to whom are we to ascribe that 
great improvement ? 
Mr. Knight, the " President," did not appear to adopt it, because by one of his 
manuscripts it was made evident that he remained perfectly satisfied with " a well- 
built and well-placed smoke flue, composed of the best materials." However, we read, 
at par. No. 1670 of the " Encyclopaedia of Gardening," (1826,) just cited, that " Pipes 
of hot water were proposed to be circulated through hothouses by Knight." (Hort. 
