454. G. W. Hawes on Diabantite in amygdalordal Trap. 
I give now a case where the pendulum was affected with a 
rapid uniform motion: each reading given below is the average 
of ten rapid readings. 
No. 5 
Readings. Diff. M’. sae M. 
101°5 23°1 , 
i pee 33°4 32°3 32°8 
1221 21 : : 
1011 41°4 us hee, SAS 
142°5 22°12 Final average, 32°14 
120°38 
The probable error is 0°44 of a scale division, corresponding 
0 s,¢s¢,050 Of an English inch. 
No. 6. 
Here each reading is the average of twenty-five rapid read- 
ings: the sign of the motion changed during the observations. 
Readings. Diff. M’. M”. M. 
92°5 53°36 ; 
83°40 51°38 : : : 
32:02 48°07 49°72 46°13 47°92 
80°09 44°19 : 
35°90 52°10 48°14 45°35 46°74 
38°60 Final average, 47°65 
49°40 
The probable error is 0-31 of a scale division, corresponding 
» ¥2,30'3,000 Of an English inch. 
When it is recollected, that with the best optical and me-- 
chanical means, it has hitherto been hardly possible to measure 
quantities smaller than ;55';)3 of an English inch, the field 
which the use of the horizontal pendulum, even under very 
unfavorable circumstances, opens, will be easily appreciated. 
Art. XLIX.— Contributions from the Sheffield Laboratory of Yale 
College No. XXXIIL—On Diabantite, a chlorite occurring m 
the trap of the Connecticut Valley; by GEoRGE W. Hawes. 
* See this Journal, III, ix, 185, March, 1875. 
