CHIMNEY-CAPS. 



229 



like a funnel, and throw the smoke into the room. 

 Fig. 187. The throat should he about as high as the ex- 

 treme tip of the flame ; if much higher, the 

 chimney will not draw so well, and if lower, 

 too much of the heat will be lost. Fi^. 187 

 shows a fire-place without a contracted throat, 

 the current of which is comparatively feeble. 

 Many chimneys draw badly by being made 

 too large for the fire to heat sufficiently the 

 column of air they contain. 



CHIMNEY-CAPS. 



When wind sweeps over the roof of a high 

 part of the budding, or over a hill, it often 

 strikes the top of chimneys below, and drives 

 the smoke downward. This may be often 

 prevented by placing a cap over the chim- 

 ney, like that represented by Fig. 188, 

 which is supported at its corners, the 

 smoke passing out at the four sides just 

 under the eaves of this cap. But it some- 

 times happens that there is a confusion of 

 currents and eddies at the top of the cliim- 

 ney, over which this cap has no influence. 

 In this case, the cap represented by Fig. 

 189 furnishes a perfect remedy, and is, in- 

 deed, perfect in its operation under any cir- 

 cumstances whatever, for the chimney sur- 

 mounted by it will always draw when 

 there is wind from any quarter, with or without any 

 fire. It has effected a perfect cure in some chimneys 

 which before were exceedingly troublesome, and were 



Fig. 



Fig. 189. 



