30 MR. JOHN GRAHAM ON CONSUMPTION 
until it appeared that I had obtained the most favourable 
condition for work, of the boiler under trial. To do all 
this required time and a considerable expenditure, as may 
be readily supposed. But the economical results which 
followed in greatly reduced consumption of coals, less fre- 
quent repair of boilers, and increased safety to the people 
employed about them, were always a sufficient motive to 
urge on the experiments. I may be allowed to say that 
the useful result in my case from these and other collateral 
experiments was a reduction of about 67 per cent. on the 
cost for coals per piece printed. 
XI. Series or ExPpeRiMENts. 
Attempts have been made to improve the boiler by en- 
larging that portion of its surface which is exposed to the 
direct radiation of the fire. A boiler possessing a contri- 
vance for that purpose came into notice a few years ago, 
and was strongly recommended on theoretical grounds, as 
it presented a very large absorbing surface as compared 
Fig. 18. 
Scale of fect 
€ Heer: 
12 6 0 
Tatastestst 
