een ee eee oF ee nT eee at Ree Re aS aN ee Cty Pe ere ee 
at the Summit of Fujiyama, Japan. 103 
be discovered, is quite uniform in its composition throughout. 
It is a part of Japanese tradition, for it can hardly be called 
history, that the mountain was produced in a single night in 
the year B. C. 286. Many geologists are of opinion that it 
is mainly the result of a single eruption. A number of speci- 
mens from the surface have been examined, and it isfound that 
when the air is retained in the pores the density is about 1°75, 
but when it is ground to a powder and the air excluded, it is 
25. These facts were communicated to five geologists, at pres- 
for the difference of latitude between Tokio and Fujiyama, 
which is about 19’, by means of the well known formula. 
When this is done it becomes 
7 t,=='999847 
From these times of vibration the part of the attraction on 
the summit, which is due to the mountain itself, is easily com- 
puted, and then the attraction of the mountain in terms of the 
density of the earth. The mountain is assumed to be a cone, 
whose semi-vertical angle is 69° and density 2°12, and its at- 
traction on a particle at its vertex is computed. Hquating these 
results the density of the earth results as follows: 
DesT7 
This result is somewhat greater than the generally accepted 
density, but when the uncertainty of some of the data is con- 
sidered it must be regarded as remarkably _ lose. 
It is believed that the density of the mountain is the most 
uncertain of all the factors, and it will be of interest to reverse 
the problem and, assuming the density of the earth to be 5°67, 
as determined by Baily, find, by combining this with the pen- 
dulum experiments, the density of the mountain. When this 
is done the result is: 
ad=2°08 
It seems to me that these experiments establish, with consid- 
erable certainty, the fact that the mountain is, for some reason, 
deficient in attraction, which leads to many questions of great 
interest concerning the possible or probable structure of the 
mountain. It is possible, therefore, that these results may be 
of some value to geologists who are interested in the structure 
of volcanoes. 
Am. Jour. Sc1.—Tuirp — Vou. XXI, No. 122.—Fes., 1881. 
