52 Report of the Select Committee 
That all boilers belonging to the engines by which such ves- 
sels shall be worked, should he composed of wrought iron 
or copper: 
That every boiler on board such steam-packet should, previous 
to the packet being used for the conveyance of passengers, 
be submitted to the inspection of a skilful engineer, or other 
person conversant with the subject, who should ascertain, 
by trial, the strength of such boiler, and should certify his 
Opinion of its sufficient strength, and of the security with 
which it might be employed to the extent proposed: 
That every such boiler should be provided with two sufficient 
safety-valves, one of which should be inaccessible to the en- 
gine=man, and the other accessible both to him and to the 
persons on board the packet: 
That the inspector shall examine such safety-valves, and shall 
certify what is the pressure at which such safety-valves shall 
open, which pressure shall not exceed one-third of that by 
which the boiler has been proved, nor one-sixth of that 
which by calculation it shall be reckoned able to sustain. 
That a penalty should be inflicted on any person placing ad- 
ditional weight on either of the safety-valves. 
4. Resolved, That the Chairman be directed to move the 
House, that leave be given to bring in a bill for enforcing such 
regulations as may be necessary for the better management of 
steam-packets, and for the security of His Majesty’s subjects 
who may be passengers therein. 
June 24, 1817. 
Mr. Doxxin’s Evidence. 
[Mr. Donkin’s description of the construction of the boiler of 
the Norwich steam-boat was similar to that given in our for- 
mer Numbers; we therefore omit it.] ; 
Is it your opinion, that any boiler so constructed was unsafe? 
—As a high pressure boiler, certainly. 
What do you call a high pressure ?—J should call from thirty 
pounds upwards high pressure ; the technical phrase is applied to 
engines where the motive force is given by the expansive force 
of the steam. 
Define what is the technical distinction between high pressure 
and low pressure engines >—When water is made to boil in the 
boiler, and confined 'so as the steam is not allowed to make its 
escape, it continues to acquire expansive force as it receives in- 
crease of heat; in the high pressure engine, the piston of the 
steam cylinder is forced down by the expansive force of the 
steam alone, against the resistanee of the atmosphere ; when 
the piston has arrived at the bottom of the cylinder, a valve is 
opened, 
