s 4 
me > . Le 
Safety Apparatus for Steam Boats. % 317 
descent metals, coals, and furnaces, to mark the melting point of . 
metals, to verify the results presented by other instruments employed 
Jn similar operations, and to answer some other peagtical and scien- 
tifie purpéSes. As the instrument would require a drawing - 
to be fully understood, a description of it is postponed to a future. 
-casion ; ‘several series of ataxev on other pomp 2 of the ee 
are Tkewise deferred. 
=. i ee 
Arr. XV.— Safety ‘ait for Steam Boats, being a doin 
tion of the Fusible Metal Disk with the common Safety Valve ; 
“by A. D. Bacute, Professor of Natural hig and Chemistry 
t the University of Fennsyiy ania. 
~ (Extracted from the Journal of the Fielkevs Institute for April, 1831.) — 
: “a the causes mere produce the ae 3 of anes boilers, 
ho one stands more prominent, whether we have regard to the fre- 
queney of the explosions caused by it, or to their violence when they. 
Sceur, than a defective supply of water within a boiler when in ac- 
tion. When the supply of water afforded toa boiler, i is insufficient 
{0 compensate for the water which is conv to steam, the level 
of the fluid within is lowered ; ; the boiler itse! comes heated, of- 
‘Keo intensely, and the steam partakes of this temperature without, 
an insufficient supply of moisture to give the dersity correspond- 
‘ig to that temperature, having a corresponding ¢ orce. 
existence of such a state of things within a boiler, : the ordinary 
safety valve gives no indication, the tension of the steam within is 
Tot sufficient to overcome the weight with which the valve is loaded; 
it not only ceases to deserve the name of safety valve, but the open- 
3 ing of it, by hand, may be the very means of producing an explosion: 
r.the escape of steam, thus permitted, relieves the water within the 
er from ‘pressure ;, the fluid rises in foam; and being thrown into 
‘ Contact with the heated sides of the boiler, tens: as is supposed 
‘Some, being projected into the hot and unsaturated steam,) is flashed 
into steam, too considerable in quantity to find a vent through the 
Valve, ‘and of an’ elastic force sufficient to defy the controlling power 
of the materials used in the construction of the boiler. The raising 
of this valve is not necessary to_ the production of an explosion in 
the — Paes a supely of water suddenly introduced 
Vou. XX. N 
