58 
IRON AND WOOD ROOFS FOR STOVES, &c. 
These facts are stated from accurate observation frequently repeated, and from 
exact calculations very severely tested ; they may therefore be considered to de- 
monstrate in the last place the decided advantages which the plan of heating by 
the circumvolution of hot water possesses over the rival system of heating by the 
diffusion of vapour. To the superiority of the water plan as to economy, both of fuel 
and labour, I may be allowed to bear witness ; for during the last fifteen years I 
have devoted the best energies of my mind to the subject. Throughout that long 
period I worked four steam boilers, and had under my own eye the direction and 
application of no fewer than six of the most approved systems for raising tempera- 
ture by means of hot water. This extensive experience, and the opportunities it 
afforded of drawing an impartial judgment on the merits and defects of all the 
systems, added to a natural taste for and love of experiment, directed me to the 
construction of my economic egg-shaped boiler, which has not only received the 
direct approbation of every engineer who has witnessed its operations, but is consi- 
dered by them, and by all who have adopted it, as the most simple and economical 
of all the plans as yet submitted to the public. So confident am I of its superiority, 
that I always offer a guarantee to all who employ me to fix it, that I will keep it 
in repair and take the responsibility of its acting properly for three years, pro- 
vided that it be fairly used. On such conditions, those who favour my invention 
cannot run much risk, nor entertain much apprehension as to its efficacy, for surely 
three years will afi*ord them ample time to decide upon its merits. Its chief features 
are, its expanse of surface, and economy of its arrangement. Aware as I am that 
any information from practical men explanatory of the cause of improper working 
in so many hot- water apparatus will be acceptable to all gardeners who have the 
management of them, and who peruse your truly valuable publication, I will briefly 
state a few of the principal causes to which failures are attributable, among which 
none are so difficult to overcome by persons unacquainted with the hydrodynamic 
principles on which the action of hot water is regulated, than the accumulation of air 
in the pipes. Indeed unless proper arrangements are made for the escape of air, which 
is evolved from water when at a boiling point, no apparatus can act properly. 
Now from some accidental cause, even in the best-constructed apparatus, this air 
may collect and lodge in the corners or angles of the pipes, particularly when they 
have to rise and fall ; this should be particularly attended to, as the want of due 
regard and necessary precaution in this particular is in my opinion the principal 
cause of the many failures with hot water, and the reason why this description of 
apparatus is sometimes spoken of unfavourably ; for I have invariably found from 
practical experience, that water will not circulate beyond the point where there is 
an accumulation of air ; and the more powerful the attempts made to remove the 
obstruction by increasing the strength of the fire, the more likely is the apparatus 
to work improperly, and to cause an overflow of water in the supply cistern. 
Therefore, as soon as it is discovered by the gardener, or the person having the 
management of the fire, that the water does not circulate regularly, he should trace 
