d14 
to make experiments and tests on any ma- 
terial, and to give to America a laboratory 
that should speedily become to our country 
what the laboratory of Kirkaldy is to England. 
Fig. 1 shows the machine now employed in 
their department of tests and experiments. 
The machine stands on two cast-iron legs, 
supported by any suitable foundation. On 
these legs there rests a framework of wrought- 
iron I-beams, so constructed as to give the 
entire structure an exceedingly solid and firm 
basis. This framework supports a system of 
levers arranged in a manner similar to that 
of an ordinary scale, only proportioned so as 
to withstand the severe stresses and shocks. 
These levers support a secondary framework, 
also constructed of I-beams, and carrying four 
columns. On the tops of these columns stands 
a heavy casting, from which are suspended two 
side-screws, carrying the top crosshead, to 
which one end of the specimen to be examined 
may be attached. These screws are simply 
used as arapid and convenient means of ad- 
justability, so that longer or shorter specimens 
can be tested. This system—namely, the 
adjusting-screws and top crosshead —is sup- 
ported upon the framework of I-beams forming 
the platform. Beneath the top crosshead is a 
second crosshead, also supported on two screws, 
which are placed inside the adjusting-screws. 
These screws extend downward through the 
platform, and are attached to two worm-gears 
firmly secured to the under side of the bottom 
framework. ‘The worm-gears may be rotated 
in either direction, at the pleasure of the op- 
erator, by means of the belt and gears at the 
right hand. ‘The worm-gears and screws form 
the straining-mechanism, capable of applying 
any stress up to two hundred thousand pounds. 
Great care is taken in the construction, so that 
no part of this mechanism whatsoever shall 
touch, or in any other way come in contact 
with, the platform, save solely and simply 
through the specimen to be tested: conse- 
quently all the stress produced by the cross- 
head on the platform must necessarily pass 
through the specimen; and only this amount, 
and no more, can be estimated on the weighing- 
beam. 
A part of the scale system may be seen in 
the front of the cut; the end of one of the large 
levers extending under the platform, and two 
smaller ones carrying the stress from the end 
of this lever to the beam. Over the larger 
one of these levers are four small columns sup- 
porting a handle and lever. This apparatus 
is a testing-machine in miniature. The full 
power of the machine may be used, having a 
SCIENCE. 
[Von. IIL, No. 68. 
capacity of two hundred thousand pounds, 
reading to ten pounds, and accommodating 
specimens up to ten feet in length ; or by means 
of the lever a force of ten thousand pounds 
may be exerted, reading to half-pounds, and 
accommodating specimens up to five feet in 
length. 
The platform of the machine occupies con- 
siderable space, being some ten feet long by 
six feet in width. As this platform is sup- 
ported on the scale, any weight which is placed 
on it must be felt by the beam; and, in order 
to test the machine, all that is necessary is to 
pile on the platform a series of standard test-_ 
weights. 
Fig. 2 is a transverse section. Here the legs 
are shown supporting the beams in the same 
way as in the previous drawing. The lower 
crosshead screws, k k, carry the crosshead 
C, while the. screws h, carrying the upper 
head, are in front of the columns 7 j. At 
the left may be seen the driving-apparatus for 
furnishing the power to the lower crosshead, 
the belt J? being arranged to slide to and fro 
on a tight and loose pulley. The tight pulley 
conveys the motion of the belt to the top driv- 
ing-shaft. On this shaft there is a set of 
three gears, arranged in a manner very simi- 
lar to the back gears of an ordinary lathe, by 
means of which three different speeds may 
be communicated to the main driving-shaft, J. 
Just to the right of these three gears may be 
seen a set of reversing-gears, so arranged, that, 
by throwing a lever to and fro, the crosshead 
may be run either up or down, at the will of the 
operator. On the driving-shaft, J, are placed 
two worms, cut, respectively, right-handed and 
left-handed. ‘These match in the correspond- 
ing worm-gears which are placed at the bottom 
of the screws k and k. The main screws are 
cut right and left handed, so as to turn in oppo- 
site directions, neutralizing all the frictional 
stresses of the crosshead, and preventing any 
tendency to twist. ~ 
Perhaps the action of the machine can be 
well understood by supposing a test-piece in 
tension. The piece is secured in the top cross- 
head, B, by wedges; the other end, secured 
to the lower crosshead, C, thereby forming the 
only connection between the platform and the 
driving-mechanism. As fast as the screws are 
turned, stress is exerted on the specimen, which 
is communicated to the platform, and weighed 
by means of the beam at the left hand. 
The results of tests are so largely dependent 
upon the skill of the operator, that very natu- 
rally much hesitation has been felt in accept- 
ing them as conclusive. It has been the aim, 
