24 MR, JOHN GRAHAM ON CONSUMPTION 
at these parts than any of the boilers of other shapes I have 
experimented with. Indeed this circumstance forms an 
objection of some weight to the boiler. The only mode I 
have tried to obviate this difficulty, was to place two blow- 
_ off pipes, one in each bend, extending at least as far as the 
length of the fire, with numerous holes in their under sides 
so that the dirt could be sucked in and discharged from 
the boiler. I have observed, apart from the injurious 
effects of dirt or scale, that any substance touching the 
boiler where it is exposed to great heat, such as cast iron, 
bricks, mortar &c., will cause, sooner or later, a serious 
deterioration of the strength of the plates at these parts. 
If these points of contact are excited by the presence of 
moisture, the deterioration proceeds with the greatest 
rapidity. 
VIII. Series or Experiments. 
Fig. 10. 
Se eae oS. fect 
7260 1 2 3 : 5 ket 
The third boiler experimented with was a plain cylinder, 
33 feet long by 5 feet 6 inches in diameter. 
