Year: 1874

scientiac Testing or steam and other


Machinery.


The case of the tugboat which exploded
her boiler on the East River will probably
soon be allowed to pass into official oblivion,
| yet the enormous multiplication Of accidents
from detective machinery and especially un-
sound boilers will lend peculiar interest to an
address on this subject by the eminent British
scientist Professor James Thomson. of Glas-
gov, which has recently been published.
There is no practical question with which the
public have moro to do and upon which ex-
listing opinions require more overhaulng
Nothing can show the ignorance prevailing
more conclusively than the wide differences in
the legal tests applied to the boilers OF passen-
ger steamers in different countries. In the
United States the by draulic test applied is,
where the engine is low-pressure only one
third more than the working pressure allowed
by law. In France the hydraulic test re-
quired is two and half or three times that
of the working pressure; and in England the
Board of Trade Surveyors use a test of double
the working pressure for which the boiler is
certified.


Professor Thomson, who has reputation
as perhaps the foremost scientific engineer OF
Great Britain, advances views Of the whole
subject of machinery testing which appear to
explode one at least of the current theories
which is undoubtedly prolific in harm. The
great argument used by boiler makers and
sellers against severe tests is that undue strain
cripples the boiler and renders it liable to
easier and earlier fracture While claiming o
theoretical strength for their workmanship
five or six times that to be required of it when
in actual use they frequently resist the appli-
cation Of even double test. Professor
Thomson strongly and pausibly contends that
the legal test should be at least three times as
great as that to which in practice tho struc-
ture is subjected, and, if the theoretical figures
of engineers are worth anything, certainly the
proposed test should not be objected to by the
boiler maker


The distinguished lecturer forcibly reasons
that ''the greater the pressure boiler has
actually borne without bursting or leakage
the greater will be its safety for the future,
and this the more so if the severe test has
been repeatedly applied without the occur
renee of rupture" A boiler intended for use
with a working pressure of fifty pounds if
tested to three times that number may posi-
bly, be impaired; but if the crucial test be
repeated three or four times no sensible man
could doubt its perfect safety when carrying
the intended fifty pounds pressure


Jn Mo,
chester, when boiler was tried with a water
test of two hundred and fifty pounds on the
square inch. the ends of the boiler breathed
outwards, but upon relieving them the iron
resumed its original position, showing no
detriment to the wrought portion. The
cast iron manhole however, was ruptured by
the strain, proving that only the wrought
iron could resist the tremendous force
brought to bear on its crystalline structure.
II we except the weaker cast lrol portions Of
o boiler Professor Thomson's test would
probably be sustained by every boiler fit to
be trusted with human life,


The great expense to which the govern
ment has put itself or boiler experiments is,
perhaps, after all only an unconscious attempt
to determine the minimum margin OF strength
to be granted certified boilers, whereas the
rule should be that none should be certified
unless they will stand some such test as Pro-
fessor Thomson proposes That the gradual
and gentle testing OF machinery to high
degree rather hardens and strengthens it than
the contrary Is strongly supported by the
facts urged by the British engineer. His
proposal extends not only to boilers but to
railroad and other bridges, floors, cranes,
ships and water reservoirs of the insuficiency
of which latter especially we have had in this
country recently such terrible Illustrations.


1t is strongly to be hoped and pressed that
Congress- at its next session, will take up this
whole subject and deal vita it in a way that
will insure security to the travelling public,
where now only suspicion and insecurity are
felt.


The Strike OF the 'LOngshoremcn.


A strike, during hard times at the opening
of winter, and when great number of men