PAPERS READ AT THE NATIONAL ACADEMY OF SCIENCE. 549 
right hand corner appears a small photograph of the trapezium alone, with only 
five minutes’ exposure. 
The second paper on the list was an extremely abstruse dissertation by Prof. 
George F. Barker, of the University of Pennsylvania, on ‘‘Condensers for Cur- 
rents of High Potential.”” The reading occupied fifteen minutes, and was followed 
by the memoir of Prof. C. S. Peirce, of the United States Coast and Geodetic 
Survey, on the ‘‘Ellipticity of the Earth as deduced from Pendulum Experi- 
ments’”—a work upon which the author has been for many years engaged, and in 
the course of which he he has arrived at some new conclusions. The experiments, 
were undertaken at the instance of Superintendent Patterson, of the Coast Survey, 
and their results, as communicated to the scientific world from time to time, have 
been highly commended by European mathematicians. Prof. Peirce began by 
alluding to some of the difficulties connected with pendulum investigations, par-- 
ticularly those relating to the coefficients of the effect of temperature and that of 
atmospheric pressure. The latter was determined in 1829 by Sabine, and still 
later, Baily, .in his review of Foster’s experiments, undertook to correct all former 
results and to construct a coherent table. The first determination of the coeffi- 
cient of the effect of temperature was that of Kater, which has long been an au- 
thority among men of science. When Prof. Peirce undertook his work, at the 
suggestion of Superintendent Patterson, he had before him the results of previous 
experimentalists. His observations have extended over a series of years, and 
have been conducted with appliances of extreme delicacy. Some of his conclu- 
sions are at variance with accepted doctrines. He finds, for example, that the 
correction hitherto made for the attraction of elevations is without actual founda- 
tion in fact. An island in the ocean, instead of making necessary a correction 
for its elevation above the general level, is without such influence as has previ- 
ously been supposed on the vibration of the pendulum, and the same principle 
applies to elevations of other descriptions. In his memoir Prof. Peirce submits. 
extensive tables of his results at different points. The paper was. discussed by, 
Prof. Peters and others. 
Prof. Agassiz followed Prof. Peirce in a description of Sigsbee’s gravitating 
trap for bringing up organisms from different sea depths and investigating the 
strata of marine life. Prof. Agassiz first described the instrument and compared. 
it with the unsatisfactory big formerly use. It consists essentially of a cylinder 
furnished with a sieve and valve at the bottom, which is sunk to the required. 
depth—1oo, 500 or 1,000 fathoms, as the case may be—filled with water. When. 
at the proper point for taking a haul a heavy ring is liberated and slides down the: 
cable until it comes in contact with a device for opening the valve. The latter 
opens and the water flows in, displacing the volume of water contained in the 
cylinder, and carrying with it marine organisms living in the stratum under inves-- 
tigation, which are arrested by the sieve and thus lifted to the surface. The result 
had then, Prof. Agassiz said, was to prove there was actually no difference be- 
tween the organisms at the surface and those living at a depth of fifty fathoms.. 
