THE FORCING GARDEN. 



525 



no instance within our knowledge of any material injury being 

 produced by the eliects of the electric fluid, but that is no 

 reason why such should never be the case. Accidents of that 

 nature so seldom happen, under ordinary circumstances, that it 

 is by no means a matter of surprise that it has not happened 

 in the case of metalhc houses, when we consider the compara- 

 tive few in number throughout the kingdom. 



Practical gardeners are, and have been, doubtful of the suc- 

 cess of such houses. Abercrombie and Speechly in England, 

 and Nicol in Scotland, excellent practical and experimental 

 gardeners, were decidedly against them, and most others have 

 avoided giving their opinion. Mr. Atkinson, who has designed 

 and built more hot-houses than probably any other architect 

 of the day, is also decidedly against them. Those who have 

 adopted them are chiefly amateurs or philosophical gardeners ; 

 some few practical men have had the management of them, 

 and one or two have built from their own designs. The most 

 e-xtensive erections of this sort are now building, under the 

 direction of Mr. Forrest, at Sion-house. " The result of his 

 success will, probably, tend to set the matter at rest." 



ON THE FORM OF ROOFS, &C. 



The form of hot-houses, till of late years, was generally that 

 of a straight front, with sloping roofs, supported in front on a 

 parapet wall, sometimes with and sometimes without any upright 

 or front sashes, and differing in their angles of elevation, to 

 suit the purposes for which they were intended, but, in most 

 instances, they were built without any premeditated design 

 thereto, or to that effect. Mr. Knight, however, about the 

 beginning of this century, revived the theory of Boerhaave, 

 Professor of Botany at Leyden, " who exemplified a principle 

 which he laid down, for adjusting the slope of the glass of 

 hot-houses, so as to admit the greatest number of the sun's 

 rays, according to the latitude of the place." 



This was adopted by the celebrated Linnaeus, and afterwards 

 enlarged upon by Faccio, Adanson, Miller, Speechly, and 

 others. In 1815, Sir George M'Kenzie introduced into no- 

 tice the hemispherical form of roof, as being supposed to be 



