15 



An interesting and valuable application of this result, were it entirely trust- 

 wortliv and were the other necessary facts in our possession, would be the determi- 

 nation of the density of the earth. While many of the circumstances are extremely 

 favorable to this end, many of the data are, unfortunately, somewhat uncertain. 

 It was originally intended to undertake at the same time a complete trigono- 

 metrical survey of the mountain in order to obtain the necessary data concerning 

 its volume and form as accurately as possible. This, liowever, we were obliged to 

 defer but it is hoped that it may be made, at some future time. The following is 

 offered as, perhaps, the most approximate solution of Ihe problem possible under 

 the circumstances. 



Fujinoyama is an extinct volcano whose height is known to be 2.34 miles, 

 very closely. It is renowned for its almost perfect symmetry of form and for 

 the fact that it lises solitary and alone out of a jilain of considerable extent. 

 Thus there is not much to consider except the attraction of the mountain itself. 

 To determine this, is, of course, a matter of considerable difficulty but it is believed 

 that a result, not far out of the way, is reached by the following assumptions. 



Without any great error the mountain may be assumed to be a cone. The 

 angle of this cone has been obtained by making careful measinements upon a 

 large number of photographs of the mountain, taken from many different points 

 of view. The mean of many measurements, whith do not differ greatly among 

 themselves, gives for this angle;— 



A = 138°.- 



Anotla-r ]'oint f'f vital iiii] i^rtance is the mean density of the nioimtain. 

 The rock, as far as can be discovered, is quite uniform in i(s tcnipositii n 

 throughout. It is a part of Japanese tradition, for it can hardly be called his- 

 tory, that the mountain was produced in a single night in the year 15. C. 2SC>. 

 Many geologists arc of opinion that it is mainly the result of a single eruption. 

 A number of S|iccimens from (he surface have been examined and it is for.nd 

 that when tlu' air is retained in the pores the density is about 1.15, but when it 

 is ground into a powder and freed fn)iii air it is 21). 



These f;u;ts were communicated to five geologists, at present employed in 

 Japan, Messrs. ^lilne, Lyman, I'rauns, Nauman and Netto, most of whom had 

 Considerable knowledge of tlie mountain from jwrsonal examination, 'i'hey were 

 requcRtcil to give an opinion as to what wiis its most probable niean densitv. 

 Tlitse ojiinions, which were based on various sui)positions concerning the internal 

 structure of the mountain, were kindly furnished and I am greatly indebted to these 

 gentlemen for the interest wliicli they exhibit«d in the problem submitted. 



The mean of these results gave for the density of the mountain ;— 



(/ = 2.12 



