588 Dr. E. Naumann—Magnetism and Earth Structure. 
towards the Japan Sea. This curve, therefore, exhibits the same 
features as the axial line of the folds, and to a certain extent the 
isogones and the fold lines coincide. In a paper published in the 
Proceedings of the Royal Geographical Society,! containing a some- 
what fuller account of the geology of Japan and of the distribution 
of magnetism in that country, I have said: “These results open 
out an entirely new field of research, and I hope that they may 
be an inducement to a continuation of similar investigations, so 
that some light may be thrown upon those still very obscure pages 
relating to the causes of magnetism and to the internal condition of 
the earth.” 
Since the publication of the above-mentioned memoir, letters of 
approval have been received from many well-known authorities, and 
a number of reviews, by no means unfavourable, have appeared. 
But in some cases I have been entirely misunderstood, and quite 
recently a violent attack has been made by Dr. Cargill G. Knott, of 
Tokio He says, that an inspection of the results of Sekino’s 
survey, carried out under my direction, convinced him that it would 
be unsafe to deduce from them any definite conclusion as to the 
general magnetic characteristics of Japan, and to him it appeared 
“that the thing to be desired was a new survey, which might be 
called a preliminary survey of all Japan.” These remarks tend to 
depreciate Mr. Sekino’s observations, and are accompanied by several 
unfounded accusations. The latter I hope to prove unjustified by 
stating a number of facts, and as evidence that Mr. Sekino’s survey 
is not to be despised, I have prepared several maps as follows: 
Plate XVIII. is a combination of Mr. Sekino’s and Dr. Knott’s 
maps, from which it will be seen that there is no essential difference 
between the lines obtained by the two observers. If they do not 
exactly coincide, it must be borne in mind that the two maps relate 
to different epochs (Sekino, 1882-83; Knott, 1887), separated by 
four or five years. In discussing the question of secular change, 
Dr. Knott ignores the fact that the rate of change varies with time 
and locality, hence his method of comparison is unsatisfactory, and 
average differences are not allowed. Apart from adverse statements, 
I do not hesitate to welcome Dr. Knott’s work, for his map is a 
good check on Mr. Sekino’s observations, and shows that Sekino’s — 
survey can stand as a Preliminary Survey of Japan. 
Plate XVII. is a combination of Dr. Knott’s map with my Tectonic 
Map of Japan. Speaking of his own map Dr. Knott says that ‘‘two 
regions are to be noted as presenting magnetic irregularities; one is 
the great mountainous region about the Fossa Magna, and the other 
is between the 38th and 40th parallels. I quite agree with Dr. 
Knott even as regards the irregularities of Northern Honsbin. They 
are mentioned in my paper on the Geology of Japan, in which I 
1 The Physical Geography of Japan, Proc.R.G.S. Feb. 1887. 
2 Cargill G. Knott, D.Sc. (Edin.), F.R.S.E., Professor and Aikitsu Tanakadate 
Professor of Physics, Imp. University of Japan, A Magnetic Survey of all Japan, 
carried out by Order of the President of the Imp. University, Journal of the College 
of Science, Imp, University Japan, vol. ii. part iii. Tokio, 1888. 
