Atmospheric Moisture to Hot-Jwuses. 285 



over the other, the cisterns must be narrower, and of course more 

 are required; indeed, in this case, trough-pipes would probably 

 be found most convenient. 



In orchideous houses and plant stoves, slate cisterns placed 

 above the pipes may be advantageously employed to increase the 

 moisture, but they never reach the temperature of the zinc cis- 

 terns, seldom exceeding 80° or 85° ; they require, therefore, to 

 be larger, and more numerous. Such cisterns are admirably 

 adapted for water plants ; and a range of them extending along 

 the whole front of a hot-house instead of shelves, would be a 

 most useful as well as ornamental addition. 



Having pointed out what I conceive to be the best method of 

 supplying moisture to the atmosphere, it remains that I should 

 say a few words on other methods of attaining the same object ; 

 and first of steaming, an operation which at present seems to 

 be greatly in vogue. 



By steaming, I mean the discharging into the atmosphere of a 

 house, in large quantities^ the steam of water heated to boiling in 

 a close vessel ; it is difficult to conceive how an operation so 

 exceedingly unnatural should ever have been devised, except 

 from a conviction of the extreme necessity of moisture, and the 

 inadequac}^ of all the ordinary means employed to provide 

 it. The device proved, at least, that gardeners began to be 

 conscious of the unnatural dryness of the atmosphere of their 

 houses, and anxious for any expedient, however unnatural, to 

 counteract it ; and, considering the state of many plant houses, 

 it is not surprising that its effects, as occasionally employed, 

 should, for a while at least, be apparently beneficial. Food, 

 though scalding hot and rather unwholesome, is better than 

 absolute starvation to plants as well as men ; but, neverthe- 

 less, it is my firm conviction, that steam is invariably injuri- 

 ous in a greater or less degree, and will speedily be found so, 

 even by those who at first have had every reason to be satisfied 

 with its effects. I have repeatedly tried it myself, under divers 

 modifications, and have never failed, sooner or later, to perceive 

 its most injurious effects. Indeed, its injuries are for the most 

 part not long in manifesting themselves. The only case in 

 which it is not evidently injurious is in large houses, where the 

 volume of air is great, and the steam is converted into vapour 

 long before it reaches the plants. For it must ever be borne 

 in mind, that steam from close boilers, and vapour from water 

 heated in open vessels, are essentially different things. Both 

 are alike liquids, and both aeriform, and there the resemblance 

 ends. Caloric in a sixfold proportion has entered into the com- 

 position of steam, in the form of latent heat, which is discharged 

 among the plants, when the steam is reconverted into vapour. 



The only modification under which I can recommend this 



u 3 



