430 H. A. Rowland—Absolute Unit of Electrical Resistance. 
the rocks in question are much like those of the Chemung, 
while the fossils, both animal and vegetable, are unquestionably 
of Chemung age. But one conclusion remains—the rocks are 
Chemung and, as already stated, probably represent only the 
lower Chemung; the great Catskill group has so far thinned 
out, that it is represented only by its upper or gray member, 
the Vespertine of Pennsylvania. 
Art. LXIl—Research on the Absolute Unit of Electrical Resist- 
ance; by Henry A. Rowianp, Professor of Physics in the 
Johns Hopkins University, Baltimore, Md. 
[Concluded from page 336.] 
em. broad, 1°8 thick and 82-7 em. diameter. As the room had 
no fire in it, the circle remained perfect throughout the experi- 
ment. The wire was straightened by stretching and measu 
before placing on the circle, which last was done with great 
care to prevent stretching ; after the experiment it was meas- 
ured and found exact to ;, mm. ‘ 
The circle was adjusted parallel and concentric with the coils 
galvanometer, but at a distance of 1-1 cm. to one side, 
in order to allow the glass tube with the suspending fiber to 
pass. The length of wire was 259-58 cm. which gives a mean 
radius of 41313844 cm. These data give G’= -151925. Pre 
liminary results were also obtained by use of another circle. 
C. meter.—To obtain the time of vibration, a marine 
chronometer giving mean solar time was used. The rate was 
onl. a second per day. ; 
e dge.—To compare the resistance of the cireult 
with the arbitrary German silver standard, a bridge on Jenkins 
plan, made by Elliott of London, was used. A Thomson gal- 
vanometer with a single battery cell gave the means of accurately 
adjusting the resistance, one division of the scale representing 
one part in fifty thousand. 
aon Fagg Se Fred Paper T have criticised the use of wooden circles val 
needle Ty Wnpebded Some te cance SE et See F 
