MAY. 
109 
upright supporting pillars are all hollow tubes, which can be stopped up at pleasure, or used 
for the conduction of the rain water into tanks either outside or inside the house. Each 
house^ is also provided with a complete ventilating apparatus before it leaves the works. 
Ihis forms the subject of a second patent, and is rapid, easily worked, and efficient. Its chief 
merit consists in a skilful adaptation of the endless screw to bear the weight of the ventilators 
and lighten the labour of lifting them. The air is also admitted at the base of the house, 
and discharged at the highest point, as shown in the accompanying figure. In this house 
the top ventilators open on both sides. In cold weather one series of the arms that connect 
the entilator with the motive bar could readily be detached, and only the warmest side 
used. Or one side could be permanently fixed in houses erected for stove plants or early 
forcing. The ventilator is pitched at a different angle to that of the house itself, to enable it 
to be opened if necessary in wet weather without admitting the rain. 4 similar arrangement 
of a travelling horizontal bar, with its connecting arms, is used to open the front ventilators, 
and the system can readily be applied to any description of building. 
The accompanying woodcut represents a full-sized section of the rib or bar which forms 
the basis of the invention. The first point about this bar is that it is T-shaped, thus afford¬ 
ing a maximum of strength with a minimum of shade. The next is the smallness of the 
scantling, so as not to obscure the light. It is made of three-quarter iron, 1 inch wide, and 
inch deep. With skilful bracing this is found to be sufficient for all ordinary houses. 
Another point is the absence of rebates. The top of the bar is quite level and smooth. 
Along its centre, at intervals of 30 inches, small screw-holes are formed. Into these a small 
bolt is screwed, about three-quarter-inch deep. 1 shows the bar with the bolt (3) inserted, 2 is 
a three-quarter covering bar, and 4 a small cap-nut, made of hard white metal which cannot 
corrode. These parts complete the metallic portion of the bar. 
The .most important part has now to be noticed. On each side of the glass a dark space, 
marked 5, will be observed. This is a strip of asphalted felt of the best quality. It forms 
an elastic bedding for the glass, and separates it at all points from contact with the iron. 
This is of great importance. Iron is not only an active conductor of heat, but is sensibly 
altered in bulk by sudden changes of temperature. It expands with heat, and contracts 
with cold: hence, if it touched the glass at any point it would probably break it; in fact, 
it does break it extensively on many metallic houses. The intervention of the felt, and the 
small space left between the two squares of glass as they lie side by side on the top of the 
bar, allow of sufficient elasticity in these houses to enable them to endure all changes of 
temperature without breakage of glass. The felt and glass meeting on the top of the 
rafter perform another almost equally important and useful function—they moderate ex¬ 
tremes of temperature in these houses. Such metallic roof-bars are probably about as cool 
and as warm as wooden ones. The felt and glass break the currents of caloric passing 
through, and insulate the two portions of the bar from each other. The strength and 
durability of the fixing power will be obvious. It is composed wholly of iron, or other 
