13 
mighty agents the volcano and the earthquake, upheaved 
tlie riven rocks, and brought their treasures to the Ught of 
day." — (Loud applause.) 
Tlie Chairman eulogised this excellent Paper, and invited 
discussion, but none took place. 
MR. HARTOP ON STEAM BOILERS AND HIGH CHIMNEYS. 
Mr. Hartop next made a communication " On the boilers of 
steam engines and the construction of engine chirtineys." He 
said: On presenting myself before a meeting at Leeds, (where 
the steam-engine is so well understood,) to make observa- 
tions on steam engine boilers, I feel some apology to be due 
from me, but I trust that, however trifling the advantage 
pointed out may be, its application in so wide a field as is 
here presented will amply repay any attention given to it. 
I need not go further back than the introduction of the 
waggon boiler by the late Mr. Watt, which, from its excel- 
lent arrangement, was the standard boiler for so many 
years, during which time a very general opinion prevailed 
amongst practical men that, whenever the length of the 
boiler exceeded four times that of its grate (say 25 feet), 
such additional length was useless, as to the quantity of 
steam produced, although a considerable degree of 
heat always passed away up the chimney. The cause of 
this I conceive to be that the heated air in these flues 
passes last, and therefore when at its coolest, through the 
side flues, by which it is brought in contact with the 
water near the surface in the boiler, and therefore at that 
point where it was the hottest ; in consequence of which 
the boiler, if made very long, might re-impart a portion of 
its heat to the air in the flues before it passed to the chimney. 
This point will, however, be better defined on our consi- 
dering the boiler now in general use in Cornwall. Before 
doing so, I may, however, be excused, for making a few 
observations on a boiler, which, from its simplicity and 
strength, is at present becoming a very fashionable one, if I 
may be allowed the expression — I mean the cylindrical 
boiler with semi-spherical ends. This, there can be no doubt, 
is a boiler of great strength, and I believe it was introduced 
at a time when engines were in use with steam at 2001bs. or 
300 lbs. pressure per square inch. This dangerous pressure, 
I am happy to inform the public, is in modem engines not 
required, the highest now in use being that for locomotive 
engines at about 60 Ibs.per square inch ; the boilers for which 
are so constructed as to render danger to the public very 
improbable. In the expensive engines of Cornwall, the 
steam used rarely exceeds SOlbs. per square inch, and in the 
high pressure engines of the best makers the steam in use is 
