228 
THE FLORIST AND POMOLOGIST 
[ October, 
even during the coldest night or day of the whole year, without the possibility of 
injury to the most delicate plant. It will be seen from the figure that the ordinary 
4-in. hot-water pipes have been dispensed with as the heating medium, and hollow 
hot-water cylinders presenting a large heating surface (as much as four or six of the 
ordinary 4-in. pipes) substituted. These cylinders present the ordinary external sur¬ 
face for radiation of heat, and, in addition, an internal surface, forming a chamber by 
means of which the external air after being brought in through valves in the front 
wall, is allowed to escape into the house at openings between the cylinders, as shown 
by the arrows. The air thus becomes warmed before coming in contact with the 
plants, and by the force of gravity is diffused through the house, escaping through 
hollow rafters by means of nicely adjusted valves into a chamber in the back wall, 
and from thence into the open air, through gratings provided for that purpose. 
There is a valve or ventilator at the top of every rafter, and a valve is fitted to each 
