156 



HEATING AS APPLIED IN HOETICULTURE. 



of his method of making joints. That it 

 was necessary that they should be perfectly 

 air-tight, is obvious ; hence the more care 

 was required in packing them. We 

 believe that his joints were what is called 

 rust joints, already noticed, and consisted 

 merely of a paste formed of iron filings or 

 borings, obtained at the iron-works, mixed 

 with sal-ammoniac and water : a collar of 

 hempen cord loosely spun is first intro- 

 duced, and when driven hard in, the rust 

 is introduced a little at a time, and also 

 packed as hard as possible. A chemical 

 combination takes place in a short time, 

 and the joint not only becomes perfectly 

 air and water tight, but is also rendered 

 incapable of separation. Spigot-and- 

 faucet joints are now universally used, 

 instead of the old flange joints, which were 

 less secure and looked ill, and were formed 

 by covering thick millboard with white 

 lead, and bringing the ends of the pipes 

 together with screws and nuts. These 

 joints are now only used in cases of altera- 

 tions ; as, for instance, if additional pipes 

 are to be attached to those already in use, 

 a saddle-joint, which is a species of flange, 

 may be employed, the heads of the bolts 

 being within the pipes, and the nuts on 

 the flange without. 



Fowler, an engineer of some eminence, 

 shortly afterwards followed Kewley, and 

 published a description of his thermo- 

 siphon in the "Gardeners' Magazine." His 

 system appears to be merely a modifica- 

 tion of Kewley's, its peculiarity consist- 

 ing in lengthening out the returning pipe, 

 by which means the water would, by giving 

 out its heat during a longer run, become 

 much heavier and colder ; and hence, by 

 flowing more rapidly into the boiler, would 

 destroy the equilibrium, and consequently 

 draw the hot water up the other leg with 

 Fi ff 165. greater rapidity. A glance 

 at the annexed sketch, fig. 

 165, will show this; and 

 also make evident how 

 very little his system dif- 

 fers from that of Kewley, 

 already described. One 

 objection to this principle 

 is, that the friction must 

 be increased in conse- 

 quence of the bends in the 

 returning pipe. 

 Weeks, a cotemporary of Kewley and 

 Fowler, has shown various modifications 



Fig. 166. 



L 



o 



0 a 

 O 



of heating by hot water. One of these 

 we shall here notice, as it was the first 

 successful attempt to secure a circulation 

 under the level of the boiler. For effect- 

 ing this end, Mr Weeks calculated that it 

 was necessary to raise the water to a height 

 above the boiler equal to the depth it 

 was intended to carry it under it. This 

 was done by using a close boiler with a 

 tube rising from the top to the required 

 height ; or where a boiler was dispensed 

 with, as in the annexed diagram fig. 166, 

 a system of pipes was placed round the 

 fire-place : a is a section of the fire-place ; 

 b is an upright tube communicating with 

 these pipes, and also with 

 another vessel c, and the 

 lowermost is connected by the 

 tube d with one or any num- 

 ber of pipes under the level 

 of the boiler at e. When the 

 fire is lighted in a, the water 

 circulates freely through all 

 these pipes as the heated 

 water ascends into the vessel 

 c, and the cold water is dis- 

 placed and flows into the 

 pipes round the fire through 

 the pipe d, from the pipes at 

 e, &c. " The substitution of 

 tubes round the fire, instead 

 of a boiler over it, is not ab- 

 solutely necessary to the suc- 

 cess of the plan, though by tubes the cir- 

 culation is greatly increased. 



"Any close boiler with the tube b attach- 

 ed to its cover, and communicating with an 

 open vessel fixed at any height, such as c, 

 having another pipe similar to d fixed to 

 it, will circulate the water from such a 

 vessel to a point below the bottom of the 

 boiler, nearly equal to the balance of 

 atmospheric pressure, or say 30 feet below 

 it." The principal use of causing water 

 to flow below the level of the boiler is to 

 enable the pipes to be carried under foot- 

 paths, and in cases where the stoke-hole 

 cannot be got sufficiently deep to be 

 rendered dry by drains. This is some- 

 times the case in low and wet places ; we 

 would rather, however, render the stoke- 

 hole dry, by building it in a tank made 

 impervious to the entrance of water both 

 at bottom and sides. Various improve- 

 ments have been made by Weeks in his 

 modes of heating, one of which is as 

 follows. The boiler used is about 4 feet 



