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engineer, is moved forward by the Working Index, and is 
left, or remains fixed at the maximum pressure attained by 
the movable Index, that is to say, it advances but does not 
recede with the movable Index, and is always at liberty to 
advance as the pressure increases beyond that of its (the 
Station Register's) last resting place ; thus, to use a homely 
phrase, furnishing a very efficient " tell tale" to the employer, 
who is able at any time, by removing the glass face in front 
of the dial, (which, it is to be observed, is furnished with 
lock and key,) to place it back in any required position, 
thereby enabling him to institute a thorough check upon his 
engine driver in this respect. 
The use of this simple expedient, the writer is persuaded, 
will be found of great practical utility, and he strongly 
recommends its introduction to all Pressure Gauges ; and 
he begs to observe to the Society, the expediency of noticing 
to Government the desirability of enforcing its employment 
(or some other equally efficient means) for controlling the 
pressure of steam used, as it will be evident from the pre- 
ceding that such an expedient would act as a very safe and 
reliable check upon the parties in charge, and would thus 
deter them from tampering with the pressure of steam; it 
would also, in most cases of explosion, define the cause, thus 
removing doubts to a considerable extent, as well as mere 
speculative theory. The following two objections may 
probably be adduced : — 
1st. It may be advanced that the safety valves are 
removed out of the control of the engine driver if ferrules 
are placed upon the screws of the balances between the same 
and the levers, and, consequently, no further check would 
be necessary. In answer, it may be observed that such an 
expedient would only partially remove the control of the 
pressure from the driver ; it, no doubt, would securely 
prevent him from screwing his valves down, but still he is 
