PROCEEDINGS. 
533 
It was shown that numerical estimates of the magnitudes of these in¬ 
ternal pressures require an hypothesis as to the increase of density with 
depth or as to the relation of density to pressure, but that any hypothesis 
not inconsistent with the above-named conditions will give pressures in¬ 
creasing rapidly with the depth to about two or three million atmospheres 
per square inch at the earth’s center. Of the various hypotheses which 
have been made, the so-called Laplacian law was instanced as of special 
interest, and a table showing the corresponding variation of density, 
gravity, and pressure with depth from the earth’s surface was exhibited. 
Mr. J. Elfreth Watkins made a communication on The 
Origin of the Railway Systems of England and America, and 
the Causes of their Differences. 
Published in part under the title “ Development of the Ameri¬ 
can Rail and Track.” Trans. Am. Soc. Civil Eng., 8vo, New York, 
April, 1890, vol. 22. 
335th Meeting. April 13, 1839. 
President Eastman in the chair. 
Forty-six members and guests present. 
The Chair announced the death, on April 8, of Dr. J. H. 
Kidder, and remarked upon the great loss to the Society, as Dr. 
Kidder was ever active in furthering its best interests. 
Mr. David P. Todd made a communication on Results of the 
Total Solar Eclipse of January 1, 1889. 
Mr. W J McGee made a cbmmunication on The Evolution of 
Serials Published by Scientific Societies. 
Published in this volume, pp. 221-246. 
Mr. Abbe made the following remarks upon the paper pre¬ 
sented by Mr. Woodward at the last meeting: 
[Abstract.] 
As I was not present at the last meeting, I take the liberty now of 
saying that I do not see how we can decline to accept the figures and 
statements which have just been given us by Mr. Woodward. 
Similar statements have been made by several other eminent and able 
students of the subject during the past ten years, and it remains only for 
us to follow these results up to their logical conclusions. 
Absolute rigidity, limpidity, and elasticity do not exist in nature. 
