244 



HEATING AS APPLIED IN HOPvTICULTURE. 



has been used to stop leaks both in iron 

 and earthenware pipes, securing it well 

 with twine or cord. Water should not 

 be put into them for a few days after the 

 joints are made, nor indeed until the lead 

 has become quite dry and hard. 



Cement of the best quality, without any 

 mixture of sand, will stand any heat com- 

 municated by hot-water apparatus. It 

 is of consequence to have it applied as 

 quickly after it is made as possible. 



Another cement for earthenware pipes 

 is thus prepared : — Mix one pint of sweet 

 milk with two pints of butter milk ; set 

 them on the fire till they are curdled ; 

 strain them, and save the curd; pound 

 some lime very fine, and, after passing it 

 through a fine sieve, mix it and the curd 

 till they become a dough ; dry the pipes, 

 and afterwards apply the cement. 



In the case of garden walls heated by 

 hot-water pipes, and indeed in pits that 

 may be for a time during winter not in 

 use, it will be well to draw off the water 

 from them, to prevent their bursting by 

 the expansion of frost. This precaution 

 is, however, unnecessary where the pipes 

 are in houses, and where the temperature 

 is not likely to fall below 32°. For 

 greater safety, all boilers should be fur- 

 nished with a waste-pipe inserted in their 

 bottom, so that the water may be with- 

 drawn when required. Should obstruc- 

 tions arise that might be difficult to over- 

 come, recourse may be had to a siphon 

 formed of a flexible tube — a gas-pipe, for 

 example. The former is, however, the 

 simplest and most effectual means. 



Stopcocks are of various constructions, 

 and are usefully employed in changing 

 the course of circulation from one pipe to 

 another. They are seldom used, how- 

 ever, for graduating the temperature, as, 

 by diminishing the internal capacity of 

 the pipe, the velocity of the fluid is 

 increased. Hood gives the following 

 data : " In most cases, a cock of 2 inches 

 diameter will be sufficiently large to 

 use with pipes 4 inches in diameter, 

 and a cock of 1^ inches diameter with 

 pipes of 3 inches ; but for very small 

 pipes, the relative proportions should 

 perhaps be more nearly equal, on account 

 of the increased friction." One of the 

 best of these is that of Mr Rogers, fig. 

 322, which has the merit of not impeding 

 the circulation, as all cocks must be liable 



to do when, on being turned, they dimi- 

 nish the opening through which the water 



Fig. 322. 



flows. To the box or hollow plug a is 

 fitted a valve perfectly water-tight, and 

 which is opened or shut by the handle 

 sliding through a stuffing-box in the end 

 of the plug. It appears, however, to re- 

 quire to be placed at the elbows or turns 

 of the pipes ; — this, unless in certain cases, 

 can be no great objection. One of the 

 most economical, and, at the same time, 

 one of the simplest modes of shutting off 

 circulation in pipes, is to have a small 

 cistern cast, to which the pipes are to be 

 attached. This cistern is to have a mov- 

 able cover, with a half-inch flange bent 

 downwards, so as to fit into a groove run- 

 ning round the top of the cistern ; and 

 this cover, when placed on the cistern, 

 and the groove filled with water, will 

 form a tight steam-joint. When it is 

 desirable to shut off one or all of the 

 pipes, a wooden or cork stopper is to be 

 put in their orifices. These, being non- 

 conductors, will prevent the heat from 

 passing from the cistern to the pipes by 

 conduction, and will completely cut off 

 circulation. Where these can be conve- 

 niently attached, no other stopper is equal 

 to them. For single pipes, sometimes an 

 oblong cistern, 1 foot in length and 6 

 inches wide, is cast on them, with a cover 

 as above ; and this is found to answer 

 all useful purposes as well as methods of 

 greater complexity and expense. In no 

 department is the apparatus for heating 

 by hot water more defective than in that 

 of stopcocks ; — many expensive and ineffi- 

 cient illustrations of them might be given. 



Fig. 323 gives a section and cross sec- 

 tion of the stopcocks we had constructed 

 especially for, and used at, Poltalloch, 

 and which are very complete, having 

 six waterways each — that is, three flows 

 and three returns. They are placed 



