182 HOT-WATER BOILERS AND PIPES. 



The unequal rate of cooling of the various sizes of pipes, 

 however, renders it necessary to consider the purpose to which 

 they are applied. If it be desired that the heat shall be retained 

 for a great many hours after the fire is extinguished, then pipes 

 of larger dimensions must be used. Where a conservatory is 

 very much exposed, and liable to fall below the minimum tem- 

 perature during a cold night, then 5 inch pipe may be used, 

 which will retain the heat longer than one of smaller size ; but a 

 double length of pipe should always be used in doubtful cases. 

 But, as a general rule, no pipe should be used of more than 4 

 inches diameter, as the larger the pipe the greater the consump- 

 tion of fuel, and more heat will be given out by 4 inch pipes, in 

 proportion to the consumption of fuel, than by pipes of any 

 other size. 



The ordinary method of arranging hot-water pipes is by 

 placing the furnace and boiler at one end of the house, and lead- 

 ing them along the front within a few inches of the wall. If 

 the house be span-roofed, the pipes ought to travel completely 

 round both sides ; if single, or lean-to house, the pipe should 

 pass along the front and return the same way; i. e., the flow and 

 return pipes should be placed beside each other, as will be seen 

 in the figures in the next section. The pipe ought never to run 

 by the back wall of a house, except there be some reason to fear 

 the entrance of frost in that quarter, which, in houses with thin 

 walls, or those constructed with clapboards, is quite likely. In 

 general cases, the heat rises with sufficient rapidity from the 

 front, to prevent the entrance of frost at the back wall, unless it 

 be near the bottom of the wall. 



In general, hot-water apparatus is so constructed that when 

 the smoke leaves the boiler, it passes immediately up the chim- 

 ney, by which an incredible amount of heat is lost. I have seen 

 the thermometer rise to 200 when placed at top of a chimney 

 of this kind, and an amount of heat thereby lost nearly equal 

 to the whole amount radiated in the atmosphere of the house. 

 This is the case with many heating apparatuses, without the 

 smallest notice being taken of the fact. On making this remark, 

 lately, to a most intelligent gardener, he doubted the fact of 

 losing any heat by his chimney ; while, on trying the thermome- 



