506 Prof. John Milne — On the Form of Volcdnos. 



VI. — Further Notes upon the Form of Volcanos. 1 



By John Milne, F.G.S., 

 Professor of Geology and Mineralogy, Imperial College of Engineering, Yedo, Japan. 



DURING- the last summer I made a journey from Yedo as far 

 north as the southern end of Kamschatka. 2 As when upon this 

 trip I saw and visited many volcanos in Yezo and the Kuriles, I 

 venture to offer a few remarks in addition to those which I have 

 already expressed upou the form of this interesting class of mountains. 



In the Geological Magazine, August, 1878, I endeavoured to 

 show that the sides of all regularly-formed volcanos are not straight 

 slopes, but have a curvature which in form is logarithmic. This form, 

 it was pointed out, was that which would be assumed by any heap of 

 loose materials such as those out of which we may suppose a volcano 

 to be built. From this it was inferred that these regular volcanos 

 were natural forms, and not forms which had been produced by the 

 wearing away of one part and the bolstering up of another, as we 

 find spoken of in treatises on volcanos and physical geology. It was 

 also pointed out that from the extei-nal form of a mountain it might 

 be possible to calculate the dimension of any interna] core. 



To illustrate these views, I used several profiles traced from a 

 series of photographs of two volcanos. 



From the volcanos which I have subsequently seen in Yezo, the 

 Kuriles and South Kamschatka, I see that my views were very 

 poorly illustrated, and had I the means when there of obtaining other 

 profiles, I feel that the case stated in the above-mentioned paper 

 might be more satisfactorily demonstrated. In looking at the illus- 

 trations which I have given, it will be observed that some of my 

 curves, although generally logarithmic in character, are by no means 

 absolutely so. By comparing the curves of each profile it will be 

 seen that the discrepancy in the fourth column is greatly due to not 

 having had any true method of fixing an axis, and it would have 

 been better to have taken the mean of each pair of ordinates and 

 treated the two sides of a profile as a single curve. 



Another point to be observed is, that if the logarithmic curve drawn 

 for purposes of comparison had been placed on profile No. 4 rather 

 than upon profile No. 2, it would have been seen to have a nearer 

 coincidence with the curvature of the mountain. 



Notwithstanding these misleading illustrations, the logarithmic 

 character of the curvature is clearly to be recognized. 



Similarity in curvature. — When in the Kuriles, I saw many beauti- 

 fully formed volcanos, and these, almost one and all, showed a slope 

 which, so far as I could judge, was similar to that upon the mountains 

 which have been shown to have a logarithmic curvature. Unfortu- 

 nately I was unable to take an outline of these mountains which, 

 for purposes of geometrical measurement, would be of any value. 

 All that I can say is that these contours appeared to have a general 



1 For my previous paper, " On the Form of Volcanos," see Geol. Mag. 1878, 

 Decade II. Vol. V. pp. 337—345, Plate IX. 



2 See Geol. Mag. 1879, Decade II. Vol. VI. p. 337, PI. IX. 



