216 Prof. E. L. Hancock : Effect of Combined 
of the arms to cause a perceptible motion. This method 
proved accurate and satisfactory. 
In making the compression-torsion tests, the upper ball- 
bearing head was placed upon the platform of the testing- 
machine with the same side up as when it was on top of the 
machine. The other ball-bearing head was left on the under 
side of the moving head of the testing-machine. In this 
position the compression specimen was inserted, and the same 
set of jaws that applied tension and torsion in the tests just 
described, applied compression when the moving head of the 
machine was lowered, and afterward applied torsion. The 
compression specimens were 8 inches long, and this length, 
after allowing 2*5 inches on each end for insertion in the 
jaws, gave a compression length of 3 inches. Compression 
and torsion were both measured on a two-inch gauge length. 
Deformations were measured with an Olsen compressometer 
and troptometer. The disposition of the specimen in the 
machine and the arrangement of the compressometer are 
shown in Plate X., although this is not a photograph of one 
of the test-pieces and the troptometer is not shown. Torsion 
loads were obtained by adding the required amount oi sand 
to the pails attached to the ends of the arms, in a manner 
similar to that used in the tension-torsion tests. After the 
required compressional load was applied, sufficient sand was 
placed in the pails to overcome the friction of the ball-bearing 
heads. 
This was indicated by a perceptible movement of the 
troptometer index. In making these compression-torsion 
tests great care was used to avoid any possible column action of 
the specimen. It is believed by the writer that no such action 
took place in the case of any tests reported in this paper. 
The torsion-flexure tests of nickel- and carbon-steel shafting 
were made by means of specially devised apparatus. The 
same arms used in the preceding tests were attached to the 
ends of the specimen. The attachment of these arms and the 
general disposition of the specimen with relation to the testing 
machine is shown schematically in PI. XI. fig. ] . The testing- 
machine, upon which the apparatus Was mounted, and which 
was used in the flexure part of test, was an ordinary tension 
machine of 20,000 lbs. capacity. The torque was applied by 
means of weights, indicated in the drawing by the arrows P x . 
The plan throughout was, first, the application of a certain 
torque, and then while the shaft was under this torque sub- 
jecting it to a flexure test. While the torque was being 
applied the knife-edge A was removed, allowing the shaft to 
turn freely over the knife-edge B. When the desired torque 
had been applied, the knife-edge B was removed and the 
