532 
PHILOSOPHICAL SOCIETY OF WASHINGTON. 
Mr. C. D. Walcott made a communication on The Strati¬ 
graphic Position of the Olenellus Fauna in North America and 
Europe. 
Published in full in the American Journal of Science, 8vo, New 
Haven, 1889, May and July, vol. 37, No. 221, pp. 374-392; 
vol. 38, No. 223, pp. 29-42. 
334th Meeting. March 30, 1889. 
President Eastman in the chair. 
Fifty-two members and guests present. 
The Chair announced the election to membership of Mr. John 
Elfreth Watkins. 
Mr. R. S. Woodward presented a communication entitled 
“ Some Mechanical Conditions of the Earth’s Mass.” 
[Abstract.] 
It was the object of this communication to adduce the grounds for the 
opinion that the earth is a viscous body, whose mass behaves under the 
action of long-continued forces essentially as if it were fluid, and is there¬ 
fore subject to internal pressures which differ little from hydrostatic 
pressures. 
It was first explained that, independently of any hypothesis as to the 
actual arrangement of the earth’s mass, five important properties de¬ 
pendent on that arrangement are accurately known. These properties are 
the surface shape, the surface density, the mean density, the relation of 
the moments of inertia expressed by the constant of precession, and the 
relation of the moments of inertia derivable from the moon’s motion. 
Collectively these properties require a peculiar symmetry of distribution in 
the mass and a marked increase in density with depth below the surface; 
they are so many conditions which must be satisfied by any hypothesis 
concerning the arrangement of the constituents of the mass. 
Turning, then, to the question of pressures to which the earth’s crust 
would be subject if it were self-supporting like a dome, it was shown that 
such pressures would be thirty times the crushing strength of the finest 
cast steel, or six hundred to one thousand times the crushing strength of 
granite and limestone. The conclusion drawn from these figures was 
that the upper strata rest with their full weight, substantially, upon those 
below, producing perfect continuity of matter (probably in the amorphous 
state) at no great distance from the surface, and generating pressures 
throughout all but the superficial portions of the mass which differ in no 
material degree from hydrostatic or fluid pressures. 
