28 



General Notices. 



particularly applicable to the heating of hot-houses by hot water, we shall 

 shortly notice it. Suppose we have a common boiler, such as used in 

 common wash-houses, and which Mr. Kewley uses in the siphon mode of 

 circulating hot water; then place another boiler within it, of such a size as 

 to leave only a few inches between the inner boiler and the outer boiler 

 all round, and support it in this position by stays, {fig. 1 .) Let this inner 

 boiler have a hole in its bottom, about one third 

 of its diameter, and let its rim be 2 in. below the 

 level of the water to be heated. These arrange- 



\\ \ I I I ments being made, and the heat applied below, a 

 \ /../.■ circulation instantly takes place, and continues ; 



the water coming into contact with the heated 

 bottom and sides of the outer boilers, rising ra- 

 pidly to the surface, and descending through the 

 inner boiler, which thus necessarily contains the coldest portion of the 

 liquid. One great advantage of this construction is, that the bottom of the 

 outer boiler, having its heat constantly carried off by the liquid, is not liable 

 to burn out. For the siphon and level modes of circulating water in hot- 

 houses, this boiler promises to be a great improvement. It is our inten- 

 tion to try a boiler of this sort over Witty' s furnace — Cond. 



An improved Boiler for heating by hot V/ater. — Sir, Heating by hot 

 water is that branch of engineering which I profess more particularly, and 

 in which I have proved most successful; having always acted upon the late 

 Mr. Tredgold's system, which I perhaps understand the better from having 

 been Mr. Tredgold's principal clerk up to the last hour of his life; and 

 I am the person who made out the original drawings (under Mr. Tredgold's 

 directions) for his paper in the Transactions of the Horticultural Society, 

 which was copied in your Magazine. (Vol. VII. p. 179.) 



Having had every opportunity of proving by the many apparatus which 

 I have had the honour to execute, as far as theoiy and design extend, 

 that such calculations as respect the surface of pipe are, beyond a doubt, 

 correct, still I think that the calculation for the size of the boiler is not 

 sufficiently clear; for a furnace may be so constructed, that although a 

 given quantity of fuel may be consumed in a given time, yet that a great 

 portion of the heat from that fuel may escape though the flue, without 

 being of service to the boiler. 



The plan wiiich I have for some time past adopted is, to vary the length 

 of the boiler with the surface of pipe required ; invariably making use of 

 a. long rectangular boiler in preference to a square or circular boiler, as it 



Longitudinal section of boiler and furnace. Transverse section, 



is ; a well known fact that the bottom surface is far superior to the side of 

 a boiler in absorbing heat-; consequently, the longer the heat is retained 



