THE TANK MODE OF HEATING. 



211 



of the boiler, as will be seen by the ac- 

 companying sketch, fig. 281, to be carried 

 along the front of the pit immediately 

 under the glass, and to terminate at the 

 extreme end of the return-tank a ; b b is 

 the boiler ; c c the tanks ; d the steam- 

 pipe. When the steam-pipe is to be used, 

 the flow-pipe from the boiler into the 

 tank is intended to be stopped. 



Our objection to the use of steam in 

 this case is, that the water in the boiler 

 must be kept at such a temperature as to 

 supply the steam-pipe at 212° ; for below 

 that point steam would condense, or 

 rather would not be generated. Such a 

 temperature as this is seldom desirable 

 wherever hot water is employed in heat- 

 ing. It would be much better to use a 

 3-inch hot-water pipe, furnished with a 

 cock, so that the water could be allowed 

 to flow through it when required. One 

 pipe, in this case, would do, as it could 

 empty itself into the return-tank; and 

 this pipe must be on a level with the 

 water in the tank, or be upon the siphon 

 principle. The former, where it can be 

 conveniently adopted, is the simplest and 

 best. Wherever the tank system is used, 

 unless for the purpose of heating borders 

 or pits for particular purposes, we would 

 recommend, as an absolute condition in 

 insuring complete success, to employ a 

 hot- water pipe in conjunction with the 

 tank, for supplying atmospheric heat, 

 and that unaccompanied with so much 

 humidity as would be given out by the 

 tank alone. 



Tanks, as we have seen, are usually 

 divided, thus forming a flow and return 

 circulation. An instance, amongst some 

 others, has been shown by F. Harrold 

 Fenn, where this mode is departed from. 

 He employs a brick-cemented gutter, 

 which passes directly round the house 

 from the boiler to it again. Another 

 rather unusual feature in this case is, 

 that the water, in passing from the boiler 

 to the tank or gutter, has to fall under 

 the level of the doorway, and rise again, 

 through a leaden pipe, to the level of the 

 gutter. This might have been avoided 

 by placing the boiler below the floor- 

 level. We state this instance, to render 

 the system practicable where it might be 

 either impossible or inconvenient to set 

 the boiler so low. The scale upon which 

 this experiment was tried was not a very 



small one ; for we find the house was 45 

 feet long and 14 feet high, and that the 

 method answered the purpose completely. 

 Mr H. states that his greenhouse (the 

 house in question) is sufficiently free from 

 damp to enable him to keep his plants in 

 safety through the winter, although the 

 tank is only covered with slates one-fourth 

 of an inch thick, but cemented at the joints. 

 Mr H. is the first person whose observa- 

 tion we have met with in a published form, 

 as to the crisp ice-like scum appearing 

 on the surface of the water in recently- 

 constructed tanks. This is a very com- 

 mon case, and arises from the lime which 

 is contained in the cement; the carbonic 

 acid contained in the atmosphere of the 

 house acts on the calcareous matter dis- 

 solved by the water, and converts it into 

 carbonate of lime. This is only injurious 

 in as far as a portion of it may find its 

 way into the boiler and form a calcareous 

 incrustation on the sides or bottom ; but 

 it may easily be removed. — Vide section 

 Boilers and Pipes. 



As connected with tanks, we may ob- 

 serve that Burbidge and Healey, in con- 

 nection with their patent boiler and fur- 

 nace, have constructed a cast-iron tank, 

 which combines the advantages of the 

 round pipes and open trough. These 

 troughs are of an oblong shape, with 

 steam-tight covers, and with valves also 

 steam-tight, to open and shut at pleasure. 

 The advantage of this is, that it admits of 

 ready means of saturating the atmosphere 

 of the house, so that a moist or dry heat 

 can be obtained to any desirable degree. 



Cast-iron gutters, of the shape as shown 

 in figs. 282 and 283, are excellent substi- 

 Fig. 282. 



Fig. 283. 



