By John Frederic Dakiell, Esq. 19 



ceeded 910. Now I believe that if the hygrometer were con- 

 sulted, it would be no uncommon thing to find in hot-houses, 

 as at present managed, a difference of 20° between the point 

 of condensation and the air, or a degree of moisture falling 

 short of 500. The danger of over-watering most of the 

 plants, especially at particular periods of their growth, is in 

 general very justly appreciated; and in consequence the 

 earth at their roots is kept in a state comparatively dry ; the 

 only supply of moisture being commonly derived from the 

 pots, and the exhalations of the leaves is not enough to 

 saturate the air, and the consequence is a prodigious power 

 of evaporation. This is injurious to the plants in two ways : 

 in the first place, if the pots be at all moist, and not protected 

 by tan or other litter, it produces a considerable degree of 

 cold upon their surface, and communicates a chill to the tender 

 fibres with which they are lined. The danger of such a chill 

 is carefully guarded against in the case of watering, for it is 

 one of the commonest precautions not to use any water of a 

 temperature at all inferior to that of the hot air of the house ; 

 inattention to this point is quickly followed by disastrous 

 consequences. The danger is quite as great from a moist 

 flower pot placed in a very dry atmosphere. 



The custom of lowering the temperature of fluids in hot 

 climates, by placing them in coolers of wet porous earthen 

 ware, is well known, and the common garden pot is as good a 

 cooler for this purpose as can be made. Under the common 

 circumstances of the atmosphere of a hot-house, a depression 

 of temperature amounting to 15 or 20 degrees, may easily be 

 produced upon such an evaporating surface. But the greatest 

 mischief will arise from the increased exhalations of the plants 



