151 
Steam-Boiler at Lochrin Distillery. 
agg re g a tc strength of these portions of iron, supposing the whole 
to be in a sound state, and allowing at the rate of 27 tons as the 
force which a square inch of good iron will sustain, that the boiler 
would withstand a force of about 8748 tons, before it would be 
torn asunder. Instead of 1 inch and Jth, let us suppose that 
the holes are perforated at the distance of 2 inches apart, and 
we shall then find that the boiler will sustain a force equal to 
about 12,724 tons, or equal to 3976 tons more. On examining 
the section of this boiler, it will be found, that its figure is not 
calculated to give strength, unless the horns or points of the 
crescent had been very strongly connected by bolts or rivets, to 
the bars crossing the arched bottom. For it is not sufficient 
to set a boiler upon cast-iron bars, and make them simply 
to embrace it by wedging with iron at the bottom, without 
fixing them with rivets, or bolts ; neither does it appear that cast 
iron is so suitable for this purpose as malleable iron. 
In explaining the immediate cause of the explosion, it has 
been supposed, that the upper ridge of the semicircular bot- 
tom of the boiler had been allowed to get into a state of incan- 
descence, when a jet of water from the feeding-pipe having (as 
is imagined) been incautiously let into the boiler, the effect of an 
additional supply of water in this critical state of things, was 
to produce a sudden and great quantity of steam, or the extrica- 
tion of gases of enormous volume, by the decomposition of the 
water, by which the boiler, as we learn, was projected into 
the air like a rocket. 
In the first trials of the boiler at Lochrin, though weighing 
upwards of nine tons, it was found to vibrate and move in its 
place with the force of the steam at the rate of about 60 pounds to 
the square inch. The pressure was then, by the express orders 
of Messrs Haig, reduced to 40 pounds upon the square inch, 
and one of the safety-valves with this load, was put under lock 
and key, and the charge of it given to the foreman of the works 
In consequence of some mismanagement, however, the pressure 
must obviously have been greatly increased. If we suppose 
the velocity of the top and sides of the boiler at the moment of 
the explosion, to have been at the rate of about 80 feet per second, 
its impetus in that case had been not less than about 720 
tons. We here calculate the cast-iron bars in the usual way, 
