318 FORCING DEPARTMENT. 



to corrode, paint will not add one day to its dura- 

 bility. It has been asserted, that although copper 

 is not liable to corrode, its verdigrease is perni- 

 cious to vegetation. But when we take into con- 

 sideration the extreme smallness of the bars and 

 surface that the water can accumulate upon, that it 

 can never collect and remain, for so long a time, on 

 so slight a substance, as to become impregnated 

 with the copper, no injurious effects to vegetation 

 can reasonably be anticipated. In fact, I have not 

 yet been able to discern any drip or moisture falling 

 from the bars. 



It has again been objected, that copper bars are 

 unfit for Hot-House Roofs, as being liable to bend, 

 to the great damage of the glass, &c. under even a 

 shower of snow. In reply to this, I will refer to 

 the Winters of 1830, and 1831, when, it must be 

 readily admitted, we had much heavier falls of snow 

 than have been known for the previous twenty 

 years. In this part of the country there was snow, 

 during 1830-1, from a foot to fifteen inches in thick- 

 ness, lying on the Hot- House Roofs, yet I can 

 confidently assert, that neither was a single pane 

 of glass broken, nor a bar bent by its accumu- 

 lated pressure, although many of them are nearly 

 1 1 feet in length. Hence, as these were suffi- 

 ciently strong to resist so heavy a weight, we may 

 naturally suppose they are capable of standing 

 against all ordinary chances of destructive wind and 

 weather. In short, I conceive, copper is the best 

 material that possibly can be used for the bars, 

 where smallness of substance and durability are re- 



