140 Scientific Intelligence. 
from the lower anterior into the upper posterior portion of the 
valve following the curved ventral edge, from which it is sepa- 
rated by a broad flattened border. This line is deeply sunken 
anteriorly, becomes almost obsolete or discontinuous in passing 
the oblique internal furrow, beyond which, in the posterior por- 
tion of the shell, it is less distinct, though clearly shown. st 
in front of and above the anterior limit of this line there is a 
slight conical protuberance. Further than this nothing can be 
made out, owing to the imperfection of the material. The 
shell is thick, with the surface finely striated concentrically. 
I have never observed a specimen of this singular little shell 
with the two valves together, but they are frequently found 
side by side in the same hand-specimen of stone. 
Length rarely more than 0°16 of an inch; usual width about 
0°10. Occurs in both even-bedded and conglomerate limestone 
of the Lower Potsdam at Troy. Collected by the writer. 
Besides the foregoing species I have from the Troy lime- 
stones several specimens of an Orthis, but too imperfect to 
describe; and also a few specimens of what seems to be an 
undescribed Lingulella, which cannot at present be dealt with 
for the same reason. 
Troy, N. Y., May 14th, 1873. 
SCIENTIFIC INTELLIGENCE. 
I. CHEMISTRY AND Puysics. 
of the torsion-balance, as an instrument for absolute measurements. 
Profiting by the information thus acquired, they constructed the 
apparatus with which to obtain the constant of attraction—and 
hence the earth’s density,—in a cellar room of the Ecole Polytech- 
nique. The lever of the torsion-balance consisted of a small 
aluminum tube 50 centimeters long, carrying at each extremity ? 
copper ball weighing 109 ms. At its center was a small mir 
ror, which reflected to the reading telescope the image of a scale 
placed 5°6 meters distant. e filament of suspension was 4? 
September, 1871. At the time of the experiment, the balance 
mercury contained in two hollow cast-iron spheres 12 centimeters 
in diameter, so connected that all the mercury could be forced 
into either or be divided between them. As improvements over 
the apparatuses used by Cavendish, Reich, or Bailly, the author 
