ANGLE OF GREENHOUSES. 



55 



gives us the greatest quantity of perpendicular rays then. If the inclina- 

 tion were forty five degrees, the sun^s rays would be perpendicular about 

 April the 6th, and September the 4th ; and as the rays would vary very 

 little from the perpendicular for several days before and after the 6th of 

 April, and the 4th of September, the loss of rays arising from reflection 

 would, as appears from the annexed table, be nearly a minimum. Ev€n 

 at the winter solstice, the loss by the obliquity of the angle of incidence 

 would be only two in one thousand more than when the rays fall per- 

 pendicularly, as appears by Bouguer's Table of Rays, reflected from glass, 

 of (me thousand incidental rays. "^Tien the angle of incidence is 



87° 30' 



584 are reflected 



60° 



112 



85° O' 



543 



50° 



57 



82° 30' 



474 



40° 



34 



80° 0' 



412 



30° 



27 



77° 30' 



356 



20° 



25 



75° 0' 



299 



10° 



25 



70° 0' 



222 



1° 



25 



65° O' 



157 







Enq/. of Gard. 



PAINTING. 



Every plant structure should be painted at least three times before it 

 is finished, so as to prevent the timber from imbibing moisture, which if 

 once in, and the paint laid over it, it cannot escape, and as a conse- 

 quence, decay, under the general denomination of dry rot, commences, 

 and going on unobserved, soon reduces the fabric to a state of ruin. 

 Upon the same principle, the best quality of timber, and that weU 

 seasoned, should only be used. More mischief arises from a want of 

 attention being paid to these two points than from aU other evils put 

 together. 



In regard to colour, much may be left to fancy, at least for the 

 last coat. WTiite is the most common, but is soon stained, and looks 

 dirty; green is very popular, but is the most expensive in the first 

 instance, and requires to be oftenest renewed, as it is less durable, 

 ^d sooner fades and looks bad. A soft stone colour is at once 

 the cheapest, the most durable, and harmonizes best with garden 

 objects. 



Hot houses should be painted at least once in ^three years ; but 



