Marcu 14, 1884.] 
in the design of the present machine, that as 
far as possible the machine should do its own 
work, thereby eliminating from the result all 
personal equation ; and, supposing the machine 
(a 
ii 
N 
ES 
I 
2 
ly 
UU 
vii 
IT 
SCIENCE. 
315 
of the machine coincide with the axis of the 
specimen. In making experiments on wrought 
iron and steel, and upon other materials which 
are more or less of a ductile character, this 
rm 
EU TTT 
S 
hy 
PP 
Stata aaa att 
AX 
Hine 
NSS 
Ne 
\ 
a 
— 
> ni 
~ 
i 
a 
AR 
AP 
ow 
' = 
f so, Ss 
= SR S| 
Ege = | 
= LI pod J — 
— -hS ES 
- == See 
—— fl | — 5 
SSeS = 
SS Sow 
= EA | 
— to 
=—==—= 
=> —{ —— 
= = SS 
SSS 
—-4 aS = 4 = ilals 
—<——$——= 1 —¥ = Y = Ta r= 
——— se =P eS ef 
i= = Gy Z ; GEsoeseieey 
—— a 
ES ee 4 
= 2 rae! All 
Yi 
| 
to be once correct, all subsequent records 
should be correct mechanically. One of the 
greatest obstacles to making accurate tests has 
been the feasibility of making the axis of stress 
objection is not a serious one, as it introduces 
but a slight error in the results. In experi- 
ments on cast-iron, cast-steel, or materials of 
a brittle character, the slightest cross-strain 
