THE TANK MODE OF HEATING. 



205 



the tank ; h underground cold- air drains, 

 in which the air from the interior of the 



Fig. 269. 



re- 



house is conveyed to the chamber g, 

 where it is again rendered buoyant, and 

 diffuses itself in all directions through the 

 openings a, as indicated by the arrows ; 

 i flow-pipe ; I return-pipe ; m boiler ; 

 n doorway." 



This house, which is 32 feet long, 9 feet 

 wide, and 7^ feet high, was heated, exclu- 

 sive of the tanks, for the small sum of 

 £2, 16s. 6d. The tank is of wood with 

 slate covering, calculated, including la- 

 bour for fixing, at £5, making the 

 whole expense somewhat under £8. This 

 house is divided into two equal parts, 

 one of which is kept at a temperature of 

 from 50° to 55° in winter, and from 70° 

 to 90° in summer; the other at from 40° 

 to 45° in winter, and from 50° to 65° 

 during summer, at a total expense per 

 annum of £4, 10s. in a locality where 

 coal is 20s. per ton. 



The advocates for the Polmaise system 

 of heating claim for themselves the merits 

 of having introduced economy in the 

 apparatus, abundance of heat, and a per- 

 fect circulation in the atmosphere of the 

 house. Now, we consider that D. T. F. 

 has shown above all these conditions com- 

 pletely complied with, and certainly with 

 an atmosphere far more pure and conge- 

 nial to the vegetation into the bargain. 



Toy s mode of tank or gutter heating is 

 described by him as an apparatus con- 

 structed on a plan which will insure a 

 temperature of 70° when a thermometer 

 in the external air indicates 20°, and the 



expense of such a structure as he pur- 

 poses, not including the boiler, will not 

 be more than about £10. Any descrip- 

 tion of boiler may be used provided it has 

 two arms, the upper one of which must 

 be connected with the flow, and the lower 

 with the return pipe. The flow-pipe 

 should rise at least 2 feet before it enters 

 the gutter, and the return-pipe should be 

 placed as closely as possible to the bottom 

 of the boiler, so that the water may pass 

 out freely. The bottom and sides of the 

 tank are formed of wood ; it rests on pave- 

 ment supported on brick piers, and slates 

 are used for a covering or top, some of 

 which are movable for admitting vapour 

 into the house. The tank is not divided, 

 as is usually the case ; and Mr Toy cal- 

 , culates that the circulation is carried on 

 • by the hot water flowing along the top, 

 and the colder water returning along the 

 bottom of the tank. This is a most un- 

 satisfactory mode of circulation, and, to 

 say the least of it, has no advantage 

 whatever. That circulation will take 

 place upon this principle is to a certain 

 extent true, but not so well as if the tank 

 were divided into two distinct spaces. 



Our chief objection to this plan is the 

 use of wood, which is a bad conductor or 

 reflector of heat ; and its application here 

 is quite unnecessary, as, if the pavement 

 were properly jointed and coated with 

 cement, and the sides done with brick on 

 edge, it would be more durable and less 

 expensive. Mr Toy appears to have 

 fallen into the mistake long generally 

 entertained, and by ourselves also, of 

 placing the boiler under the level of the 

 circulation. Hood has proved the fallacy 

 of this theory, and we have also had 

 practical proofs of its inutility, not only 

 in respect of its not increasing the rapi- 

 dity of the circulation, as it was long 

 thought to do, but also of its causing an 

 unnecessary degree of pressure on the 

 boiler. Where water is carried along the 

 front of a house, as in this case, and has 

 to return in the same line, it is best to 

 divide the tank ; but where it makes the 

 circuit of the house this is unnecessary, 

 as the terminating end serves for a return, 

 the water being by that time so reduced 

 in temperature that it enters into the 

 boiler freely. We may here observe, 

 that many have been deterred from carry- 

 ing the tanks, gutters, or pipes, round 



