Improvements in heating by hot Water. \ 7 



Art. VI. An Account of some Impro-vements made in the Ap^ 

 paratiis for circulating hot Water in Hot-houses by Messrs. 

 Cottam and Hallen, of Winsley Street, London. ' By Mr. 

 George Cottam, F.H.S. 



Sir, 



As the heating of graperies and vineries by the circulation 

 of hot water is every day becoming more general, you may 

 perhaps deem any improvement in the apparatus for that pur- 

 pose worthy of record in your journal. No new scheme was 

 ever brought to perfection at once, and therefore it is not to 

 be wondered at, that some of the boilers and pipes recently 

 erected for the purpose of circulating hot water, should have 

 failed in supplying a sufficiency of heat, not merely for the 

 purposes of forcing grapes and peaches, and growing pines, 

 but even for the less difficult object of warming a green-house 

 during frosty weather. 



In examining some of the houses alluded to, it would ap- 

 pear, by the shape of the boiler generally adopted, a square 

 or oblong tank, that it was requisite the boiler should hold a 

 great quantity of water. This, however, is not the case, for 

 I have proved, both by experiments made with the tin and 

 copper models, which you have examined here (see Vol. III. 

 p. 474.), and also by hot-houses of different descriptions that 

 I have heated with hot water, that a large quantity of water 

 is by no means required. The water is merely the medium 

 through which the heat passes from the fuel consumed to the 

 atmosphere to be heated ; therefore, the quantity of water re- 

 quired in the boiler is no more than what will cover a surface 

 sufficient to receive the heat from the requisite portion of fuel 

 consumed beneath it. 



The boiler, of which I enclose you a section (fg. 24.), is 

 of a shape the most advantageous for this purpose : it ex- 

 poses a greater surface to the fire than any other form ; and 

 what deserves particular attention is, that this surface is in 

 the best possible situation for receiving the greatest quantity 

 of heat from burning fuel. It is observed by Mr. Tredgold, 

 in his excellent Treatise on the Steam Engine (p. 122.), that 

 as the fire, or bottom, surface of a boiler is the most effectual 

 heating surface, it should be of sufficient area to receive the 

 whole effect of the fire ; while the flue surface, or sides, may 

 receive the heating effect of the smoke. By narrowing the 

 top of the boiler {a), the heat received from the fuel is im- 

 mediately conducted from all points of the bottom surface {b) 

 to the entrance of the pipes (c), through which it is to be cir- 

 culated. In consequence of this, there will be less accumu- 



VoL. IV. — No. 13. c 



