Al, B, Quinby on high and low pressure Boilers. 313 
by the nathoes 
and Pe lorophtHl: Boney of the Ci ak - 
vestigate the causes which gave tise t0 the pe 
boiler on board the Steam-Boat Aitna.* 
To determine the comparative eligibility othe: high and 
the Jow pressure steam-engine, the two following 
pear to me necessary to be considered. Fir 
of each engine to explode ; and sebthidly; the danger, or 24 
injury, which each engine’ is capable of producing i incasean * 
explosion takes place. 
To determine the comparative liability of the two engines 
to explode, it will be necessary to consider the four paowing 
things :—the diameters ofthe boilers used in thet es 3 
_. the elastic force of the steam in each boiler 5 the tenacity of 
the metal of which the boilers are. Bie tiis: he thick- 
ae ness. of each boile: 
The diameter ats the boiler on board the = a ec thirty 
inches ; an the diameter of a boiler ‘for a low pressure 
engine of ae power would be about ‘ninety inches; or 
three times as grea 
stic force of abewsti in the boiler of the Atna waS 
usually 150 Tbs. per square inch; and the. elastic force of 
steam ima low pressure bgiler is -usually 10 Ibs. per. — 
it 
h. 
The tenacity of the métal of which 
is about 60,000 lbs. ; or six-seventi 
iron.} i 
- As, however, the cylinder which const 
is not solid metal, but is composed of plates 
it will be necessary to diminish the number which expresses 
the tehacity- 
Let, ISNA: the tenacity be put at 30,000 ys place 
of 60, 
* 
* The communication was *made at the request of Dr. Dekay, chair- 
man of the committe 
‘The tenacity of on metal is usually expressed the byt greatest weight 
in Ibs. which a bar one a square, of that metal, is capable of sustain- 
ing when pulled endwis 
Voi, TX. No.2. ° ™& 40 2 4 
