ON THE MERITS OF IRON AND WOOD FOR ROOFS. 83 



pipes of too large or too small dimensions are equally to be 

 avoided, and this for reasons which I could easily adduce, were 

 it not that I desire on this occasion to conline my remarks to 

 boilers formed of a series of pipes, varying from half an inch to 

 two inches, which I admit have a great advantage over boilers 

 containing large bodies of water, in as much as they become hot 

 much more quickly, but then it must be recollected, that the 

 larger body when once heated, will remain hot twice or three 

 times as long as the other. And I have proved by observation 

 that a 4 inch pipe, which contains double the quantity of water 

 which a 2 inch pipe is capable of receiving, in a house of the 

 same temperature, will retain its heat for more than doable the 

 length of time. Moreover, when boilers are used that have such 

 small water way and small pipes, they require more attention, 

 and cannot be left at night with the same safety as boilers and 

 pipes containing larger bodies of water, seeing that the former 

 cools so much more rapidly than the latter. Nevertheless, to err 

 in the other extreme, by having boilers and pipes to contain very 

 large quantities of water, would be a great waste of fuel and by 

 no means calculated to answer to the satisfaction of all parties, 

 so well as a boiler and pipes of a medium size ; it is my opinion, 

 therefore, that in neither boiler nor pipes should the water way 

 be less than 3 inches, nor more than 4 inches, and the boiler 

 should be so constructed without complication as to expose the 

 greatest possible surface to the action of the fire, this would be 

 found the most economical shaped boiler for fuel and effect, for 

 I have always remarked, that the great object of all persons who 

 heat their houses with hot water, is the saving of fuel, &c, which 

 is very considerable, when compared with the expense attendant 

 on a badly constructed flue, moreover, an opportunity is offered 

 of heating several houses at the same, or very little more expense : 

 this I have always considered of the greatest importance, parti- 

 cularly, when a gentleman's establishment is situated a great 

 distance from coal mines, and in all my arrangements with hot 

 water I have always continued to have the body of water in the 

 pipes which run through the house, as it is there that the gar- 

 dener requires a permanant and lasting heat, this it is that induces 

 me to advocate the use of 3 inch and 4 inch pipes. Moreover 

 there are great objections to the use of small pipes varying from 

 half an inch to two inches, particularly when the boiler (as is the 

 I 'Ian of some) is formed of a scries of pipes, in such cases their 



