POLMAISE MODE OF HEATING GREENHOUSES. 



126 



tjur anthracite will be found to afford an 

 excellent steady fire, easily managed. It 

 should be built with precision, and in a 

 workmanlike manner, to insure against the 

 escape of gases into the air chamber, and 

 thence into the house. Though in the 

 plans we have presented, the furnace is 

 placed under the floor of the green-house, 

 (the mode securing the greatest economy 

 of heat,) it is quite as frequently placed 

 wholly in the back shed, with an opening 

 in the back wall of the green-house for trie 

 emission of the heated air.* 



We conclude this article with two work- 

 ing plans of the furnace, showing its con- 

 struction for a hot-house of moderate size, 

 with the measurements given in feet and 

 inches. Following this, any skilful me- 

 chanic may erect a Polmaise furnace with- 

 out further directions. It is Mr. Meek's 

 latest plan; and we copy it, with Lindley's 

 remarks, from the Gardeners' Chronicle. 



We are much indebted to Mr. Meek for 

 the following plan and description of his 

 Polmaise apparatus, with the latest im- 

 provements. The plan is now given of 

 such a size, and in such detail, that any 

 village brick-layer may construct it without 

 difficulty or uncertainty. The iron work 

 he can procure of his ironmonger. We 

 strongly advise the public not to attempt to 

 improve upon this, which is the result tf 

 careful experiment and long experience ; 

 but to attend to every part of it with the 

 niost scrupulous exactness. The multitude 

 of houses, and other buildings, now suc- 

 cessfully heated upon this plan, and the 

 beautiful condition of the plants in them, 

 have finally disposed of the objections made 

 first to the principle, then to the action, and 

 lastly to the safety of Polmaise. 



Explanation of Wood-cuts. 



A. Four 4i inch brick piers on which 



* A brick furnace is no doubt the best, as retaining the heat 

 iongier, and as bein? more uniform in its temperature; and 

 that described in tne following page is a very complete one- 

 There is an ar-tighl stove, for anthracite coal, which has re- 

 cently come into use in New- York, wliicli gives a very mild 

 and steady heat withasmall consnmplion of fuel, and which, 

 we lliiiik, might also be used for Polmaise heating. 



the stone slab B B is supported, 9 inches 

 from the floor of the hot chamber. 



BB. York flagstone, 3 inches thick, 3 

 feet square, on which the stove is built. 



C C. Ash-pit, 9 inches deep ; the stone 

 forms its floor ; under this the chief portion 

 of the cold air passes on its way up the 

 sides of the stove, and by this means much 

 heat usually lost in the ash-pit is econo- 

 mised. 



D D. Ash-pit and furnace door (cast iron,) 

 J- or f inch thick; they are 11 inches long, 

 6 deep, and 9 wide, like boxes without 

 bottoms laid on their sides ; they have a 

 flange 2 inches deep all round their edge 

 at bottom, which fits into the centre joint 

 of brick work of the stove ; thus any exha- 

 lation of gas, when fuel is supplied, is pre- 

 vented escaping into the chamber; these 

 doors extend 4^ inches into brick work of 

 stove, 2 inches across the area between 

 wall of stove and that of stoke-hole, and 

 41 inches into wall of stoke-hole = ll inch- 

 es. Thus these two walls are separated, a 

 draft of air constantly flowing up between 

 them ; if the furnace door is thought too 

 shallow it can be made 8 inches deep in- 

 stead of 6. 



E E. Furnace. 1 foot 9 inches deep, 1 

 foot 6 inches wide ; stove built of Newcas- 

 tle fire brick, set in fire clay. The brick 

 work must be carefully done, every course 

 puddled in with fire clay, and the joints 

 of brick work properly broken ; the outside 

 parged with best hair mortar and cow- 

 dung. 



F. Cast iron plate, 1 inch thick, 2 feet 

 square, should be cast six mordhs before 

 using. It forms the top of furnace. Its 

 size allows it to rest 3 inches on the brick 

 work of stove ; on its upper surface, 2 inches 

 from the edge, is a rim or rib, either cast 

 on the plate or formed of \ inch cubic bar 

 •iron, slightly fixed by screws to the plate 

 itself. The course of brick work on which 

 the plate rests must be worked very true, 

 to give the plate a level bed. 



G. The cast or wrought iron rim, the 

 use of which will be presently described. 



H. Four thin pieces plate iron, i inch 

 thick, about 6 inches wide, to be used thus: 

 After the plate is laid on, the outer course 

 of brick work of stove must be brought up 

 level to it exactly, either by tile or other 



