262 REPORT UPON THE ACTION OF A TUBULAR BOILER. 



I also enclose for inspection a dozen of my little one-handed 

 crane-necked hoes, which long practice has taught me are inva- 

 luable in thinning crops, loosening the surface of the soil amongst 

 seedlings, and the surface of the pots, &c. &c., routing out in- 

 sects, their broods, and larvae, and thereby admitting readily a 

 free circulation of air to the roots. 



XXXIX. — A Report upon the action of a Tubular Boiler, 

 erected in the Garden of the Society. By Mr. R. Thompson, 

 Superintendent of the Orchard and Kitchen Garden Depart- 

 ment of the Society's Garden. 



It being the opinion of many persons of experience that great 

 advantages as a heating apparatus are possessed by tubular 

 boilers — that is to say, by boilers consisting of coils of tubes 

 containing water — it was determined by the Garden Committee 

 to have one erected in the garden. The following is the result 

 of the trial : — 



A tubular boiler was fitted up early in 1844, to heat the 

 curvilinear vinery, and the pits in the melon-ground adjoining. 

 One of the tubes which form the bottom of the fire-place gave 

 way in the summer, but was replaced by the maker. Towards 

 the end of the season the boiler again became so leaky as to be 

 totally unfit for use. Perhaps the liability to leak of this kind 

 of boiler may not be general ; but, independently of that, it is 

 necessary to mention the following facts respecting its working 

 when sound, which were ascertained in the course of the season. 



It was found to be powerful enough ; and in this respect the 

 testimonials of the constructor can be sufficiently corroborated. 

 But it is only adapted for such purposes as require a strong fire 

 to be constantly kept up, and not for horticultural purposes ; 

 for although the latter may require occasionally the command 

 of powerful heat, yet the smallest possible action is very fre- 

 quently all that is necessary. At one time the external tempera- 

 ture may be 50° below that which the house ought to be, and at 

 another time not more than 5°. By a strong draught, with fresh 

 supplies of fuel, and the attendance of a stoker, the boiler in 

 question could be made the means of counteracting the 50° ; but 

 if the draught be reduced with the view of causing a slow and 

 prolonged combustion, such as would only be required for coun- 



