Prof. J. Milne — On the Form of Volcanos. 



341 



Fusiyama and Kumagatake, I have been able to obtain large photo- 

 graphs, — of the former no less than thu'ty different views. As these 

 pictures, which have a slight distortion due to perspective, were the 

 best representation of the true form of a volcano which I could 

 obtain, it has been assumed that they are correct, and they have 

 been used in determining the shape of the mountain in the following 

 manner. To investigate the form of these mountains it was first 

 required to find an axis for them, which was attempted by drawing 

 verticals through some objects, and their reflections, which happened 

 to have been photographed in the foreground of one of the pictures. 

 Afterwards it was found better to make tracings of the photographs, 

 which were doubled until a greater portion of the profiles coincided, 

 and then to take the crease in the paper as being the median line 

 and axis. 



Enlarged drawings made by a pantograph were also used, but 

 these were found not to be so convenient as the tracings from the 

 actual photographs which are represented on the accompanying 

 sketch. In the cases which are represented, with the exception of 

 one or two slight excrescences which are shown by shading, the 

 profiles are coincident with a free curve. Whilst looking at these 

 profiles it must be remembered that any apparent differences in 

 curvature, which may be observed, are due to the fact that one 

 profile may represent only the upper portion of a mountain, whilst 

 another may give a view from the summit to the base. Thus, for 

 example, profile No. I. only shows the upper portion of profile No. 

 II. The next thing which was done was to draw a series of ordinates 

 at 5"™ apart, the length of each of which r, was accurately measured, 

 and may be seen in the first columns of the following tables. In 

 the second column, the sum of each successive pair of these ordinates 

 R is given, and in the third column their difi"erences dr. 



Now it is found, as will be seen by looking at the fourth column, 

 that-^ is equal to a number which is nearly constant, which is the 

 peculiarity of a Logarithmic Curve. 



Profile No 

 Fusiyama, from near 



Left Side. 



dr 



I. Plate IX. 

 Marajama. S."W. side. 



Eight Side. 



E 



dr 



4-60 



5-55 



6-25 



7-50 



8-55 



9-60 



10-90 



12-20 



13-60 



15-35 



17-50 



20-70 



10-15 

 11-80 

 13-75 

 16-05 

 18-15 

 20-50 

 23-10 

 25-80 

 28-95 

 32-85 

 38-20 



-95 

 •70 

 -25 

 -05 

 -05 

 -30 

 •30 

 -40 

 -75 

 -15 

 -20 



10-67 

 16-85 

 11-00 

 15-28 

 17-28 

 15-76 

 17-76 

 18-42 

 16-54 

 15-27 

 11-94 



4-70 



5-75 



6-65 



7-70 



8-65 



9-75 



10-80 



11-95 



13-20 



14-55 



16-00 



17-60 



19-25 



21-00 



E 



dr 



E 

 dr 



10-45 



•05 



20-9 



12-40 



•90 



13-7 



14-35 



1^05 



13^6 



16-35 



•95 



17^21 



18-40 



1-10 



16-72 



20-55 



1-05 



19-57 



22-75 



1^15 



19-78 



25-15 



1-25 



20-12 



27-75 



1-35 



20-55 



30-55 



1-45 



21-06 



33-60 



1^60 



21-00 



36-85 



1^65 



22-33 



40-25 



1^75 



2200 



