By John Frederic Daniell, Esq. 7 



for placing them in the ground, as well as for transplanting 

 trees; the atmosphere at that season being saturated with 

 moisture, is not found to exhaust the plant before it has 

 become rooted in the soil. 



Over the absolute state of vapour in the air we are wholly 

 powerless, and by no system of watering can we affect the 

 dew-point in the free atmosphere. This is determined in the 

 upper regions ; it is only therefore by these indirect methods, 

 and by the selection of proper seasons, that we can preserve 

 the more tender shoots of the vegetable kingdom from the 

 injurious effects of excessive exhalation. 



Radiation, the second cause which I have mentioned as 

 producing a sudden and injurious influence upon the tender 

 products of the garden, is one that has been little understood, 

 till of late years, by the natural philosopher ; and even to this 

 day has not been rendered familiar to the practical gardener ; 

 who, although he has been taught by experience to guard 

 against some of its effects, is totally unacquainted with the 

 theory of his practice. Dr. Wells, to whose admirable 

 Essay upon Dew, we are so much indebted for our present 

 knowledge upon this important subject, thus candidly re- 

 marks upon this anticipation of science : " I had often, in 

 " the pride of half knowledge, smiled at the means frequently 

 " employed by gardeners to protect tender plants from cold, 

 "as it appeared to me impossible that a thin mat or any 

 " such, flimsy substance could prevent them from attaining 

 " the temperature of the atmosphere, by which alone I 

 ". thought them liable to be injured. But when I had learned 

 " that bodies on the surface of the earth become, during a 

 " still and serene night, colder than the atmosphere, by 



