ay REPORT—1896. 
TABLE I.—continued. 
cpl 5 . | Deviation of separ 
bon f Distin- Observed Mean value of; obderven Grea Deviation in 
r “Bat & guishing Observer area in | observed area ean EAT per cent. 
BE Letter sq. in. in eq. in. | value in eq. in. | Of mean value 
Flat B W.C.U. 1:0157 —-0001 01 
H. 8. H. 8. | 1:0180 10158 +°0022 + 22 
| J. A. E. 1:0120 — ‘0038 —°37 
i | D. 8. C. 1:0175 +:0017 +17 
Round F W.C. U. 1:2230 — 0008 —‘07 
A. B. W. K. | 1:2230 12938 — 0008 —'07 
T.H.B. . | 1:2262 a +0024 +°'20 
J.G.. 1:2230 — ‘0008 — 07 
Round E W.C. U. 1°2252 +0020 416 
H. 8S. H. 8. | 1:22125 12232 —°0019 —'16 
J.A. E. 1:2250 ary +0018 +°15 
D.8.C.  . | 1:2213 —-0019 —-16 
Round L W. C.U. 0°4412 +0009 +-20 
A. B. W. K. | 0°4394 —°0009 —°20 
T. H. B. 0°4418 0°4403 +0015 +34 
J.G.. . | 04390 —0013, —-30 
D.8.C. . | 04400 —-0003 — ‘07 
iw rae tee = Is 
Round Kk W.C.U. . | 0°4418 0 0 
H. 8. H. 8S. | 0°44179 0-4418 | 0 0 
J.A.E. . | 0°4418 0 (0) 
D.S.C.  . | 0°4418 0 0 
Il. Variations in each Observer's Results of the Measurement of Eaxten- 
sion for a given Interval of Load. 
In the following table have been arranged the greatest and least 
measured extensions by each observer on each bar, for an increment of load 
of 1} ton in the case of some bars, and of 2} tons in the case of other 
bars. For the rectangular bars A, B, the extensions were measured for 
increments of 23 tons load, corresponding to stress increments of about 
21 tons per sq. in. For the 1}-in. round bars E, F, the load increments 
were 24 tons, corresponding to stress increments of about 2 tons per sq. in. 
For the 3-in. round bars K, L, the load increments were 1} ton, corre- 
sponding to stress increments of nearly 3 tons per sq. in. For each 
observer’s measurements on each bar the mean extension for the same 
increment in his set of observations is also given. By comparing each 
observer’s maximum and minimum values with his mean value, an indica- 
tion is obtained of the magnitude of instrumental or observational errors * 
in each case. 
As this comparison is not affected by error in the determination or the 
calibration constant of the instrument, it is an index of the observational 
or instrumenta! error of particular extensometer observations. 
