36 
SLATE FOR HORTICULTURAL PURPOSES. 
night ; and modern practice appears, at length, to conform to his precepts : thus, 
in the "Calendar of Operations" (Gardeners' Chronicle), we find weekly, 
cautionary hints to that effect — as, for instance, in the floral department: — " Let 
the temperature by night be kept as near as possible at 60°, increasing it by day 
15° or 20° ;" and in those of the pines and vinery, — " day-heat, 75°, allowing the 
glass to reach 85° in sunshine, and to fall to 65° at night." We err greatly in 
practice and opinion, when we insist upon the necessity of retaining high excite- 
ment during darkness ; for, in the first place, the physical condition of a plant 
is not the same as when it is under the attractive and elaborating stimuli of the 
rays, nor does cold affect a plant very materially during the night. On the 26th 
Jan. 1842, during a violent gale of wind, a chimney-shaft was blown over, and 
many bricks broke through two large lights of a hothouse, then under forcing ; 
fifty squares were destroyed, besides wood-work : the fire would not act : cold 
came on after the storm ceased, and yet, a reduction of heat to 50 , or less, did 
not cause the slightest injury to the tender shoots of a vine ! 
Still, it is not advisable to encourage great transitions, although it is yet more 
erroneous to maintain 70° or 75° at a time when weak and useless elongation of 
the cellular, moist parts of a plant, must be the only natural result. 
SLATE FOR HORTICULTURAL PURPOSES. 
In the management of a garden every thing that tends to produce a greater 
degree of neatness than has been previously displayed, or economises expenditure, 
is sure to be hailed as an acquisition equally important with the discovery of an 
improved method of treating any individual species, or tribe of plants. For as 
the chief end of all gardening is to bring together, and dispose tastefully, an 
assemblage of beautiful objects, it is essential that all the minor accompaniments 
be such as will most harmonise with, and enhance the character of the more 
prominent features ; and the desirability of effecting this at the least possible 
expense is a consideration that, we may confidently assume, none will be disposed 
to underrate. 
It should be borne in mind, however, that it is not that which may be had, 
or can be done, at the lowest primary cost, which always ultimately proves the 
least expensive ; but that which unites present efficacy, and the capability of con- 
tinuing it, at the least outlay. The material, to the consideration of which the 
present paper is devoted, in some of the different forms in which it has been 
applied to horticultural purposes, we are willing to believe, possesses a capacity 
for furthering both these points. 
The application of slate, by Mr. Beck, of Isleworth, to the manufacture of 
boxes for the reception and growth of conservatory plants of large size, which 
