On Heating by Hot Water, 



in the building. The laws both of cooling by the glass and of radia- 

 tion from the pipes have been so ably and accurately treated by 

 Mr. Charles Hood in his most valuable treatise on hot water 

 apparatus, that there is now nothing to desire on this head. An 

 apparatus may be adjusted with the most minute accuracy to the 

 work required of it. Formerly the most preposterous blunders 

 were committed on this point, — almost all the earlier apparatus are 

 incompetent to the work required of them, the quantity of pipe 

 being utterly insufficient to produce the heat desired, while the 

 boiler being large and of very defective construction, a vast quantity 

 of fuel was burnt to waste ; the gardener finding his heat de- 

 ficient naturally stokes up his fire and throws on fuel in the hope 

 of increasing it, but the only result of his labour is the more 

 rapid destruction of the boiler itself. Until the publication of 

 Mr. Hood's work above mentioned, the principle of circulation in 

 hot water apparatus, was very little understood, most erroneous 

 notions prevailed on the suject, and where the principles were 

 unknown, and opportunities of experiment comparatively few, it 

 was not to be wondered that practice was very defective. It 

 must however be observed that if the earlier apparatus were mostly 

 deficient in the quantity of pipe employed, many of those more re- 

 cently erected err in the opposite extreme. The error arises not 

 from any defect in the data or in the calculations, but from assuming, 

 as the minimum of external air, a temperature which very rarely 

 occurs in this country, and which lasts for so very short a time that 

 no building has time to cool down to a corresponding temperature ; 

 the gardener is generally consulted as to the heat he requires, and 

 if he states, as he probably may do, that he wishes to keep his 

 greenhouse at fifty degrees and his stove at sixty-five degrees when 

 outer air is five degrees or 0° the apparatus is constructed accord- 

 ingly, and will of course be found excessive in power ; a power of 

 thirty degrees for greenhouses and of forty-five degrees for hot- 

 houses will I believe be found ample under any circumstances in 



