666 



THE COMPLETE GRAZIER. 



BOOK VIII. 



Assuming a yard of 60 feet by 45 feet, divided into two, and enclosed 

 by buildings on the north and east sides, Mr. Moscrop by means of a 

 section drawing shows that the eaves openings on the west slope out- 

 wards and upwards, and tend to throw upwards the current of air enter- 

 ing the yard. These openings are returned round the east side : but 

 buildings being supposed to exist here, the open spaces are got between 

 the eaves of the two roofs, piers being built on the walls to give the 

 necessary height to the inner one. 



The air-current on these sides, it will be observed, is turned down- 

 wards ; but practically little inconvenience arises from this, the adjoin- 

 ing roofing affording protection from anything except very strong gales 

 and drifting snowstorms. A cheap and simple contrivance, used to 

 obviate this occasional drawback is made of pieces of half-inch board, 

 about the width of the opening, suspended from the eaves between the 

 piers by pieces of light chain. They are dropped when a storm occurs, 

 and afford very effectual protection, and are readily looped up again 

 out of the way when the storm abates. Seldom more than one side 

 of the yard needs protection in this way at one time. 



The diagram (fig. 197) shows an ordinary queen-post truss, strong 



Fig. 197. Section of Root Showing Sir H. M. Thompson's Mode of 

 Ventilation, the Covering being Slates or Tiles. 



enough to carry a covering of slates or tiles. To get a ventilating 

 opening high up in the roof, the queen posts are lengthened as shown, 

 the clear space of a foot or fifteen inches thus obtained inducing a free 

 current of air across the yard, and through its entire length, without 

 any draught being felt below. The currents from the gables are 

 obtained by leaving openings in them at the same level as the break in 

 the roof and eaves openings. The spars on the upper part of the roof 

 overhang the lower, and thus exclude rain and snow. 



The foregoing embodies the principle of " roof ventilation " referred 

 to, which the late inventor said that, " until he was better informed, 

 he would take leave to call perfect." After many years of experience 

 in the construction of covered yards, Mr. Moscrop has no hesitation in 

 endorsing this assertion, and in no instance where it has been adhered 

 to has he seen anything but the most complete success. 



Fig. 198 shows section of a roof-truss designed for slates to be laid 

 in a way known as open slating. This mode of covering has been 

 rather extensively adopted, and, with the eaves openings as shown, the 

 ventilation obtained is fairly satisfactory. It will be seen from the 

 sketches A and B (fig. 198), that there is a free space for the passage of 



