m 
CONSTRUCTION OF HOT HOUSE ROOFS, 
The roof is supported by 
two rows of cast iron pillars, 
one row along the front and 
end, as d, and the other along 
the centre of the house, as c. 
These pillars are placed six 
feet and a half apart in the 
rows, and are each three inches 
diameter ; the front ones are 
made hollow, so as to admit a 
leaden pipe, which carries off 
the water from the roof into a 
drain laid in the gravel walk, 
on the outside of the house ; 
this entirely does away with 
the appearance of a spout. At 
the bottom of the iron pillars 
there are socket (e) which are 
let into the stone, and give the 
pillars firmness, and through 
this socket the pipe descends 
into the drain. 
IXC 
