Dr. E. Naumann—Wagnetism and Earth Structure. 541 
masses of molten matter have been ejected from these clefts, and it 
is not difficult to imagine that such enormous fissures have some 
influence upon earth currents, and consequently on the magnetic 
needle. 
My former remarks on the reduction of the declination values to 
one hour are said to contain a “slight” inaccuracy, and Dr. Knott 
seems to think that no correction was applied to observations made 
at the northern stations. On this supposition he depreciates Sekino’s 
observations, and, together with the supposed injudicious distribution 
of stations, it is used as an argument against the first Magnetic Survey. 
The title of Sekino’s Magnetic Map of Japan, which was exhibited 
at the Berlin International Congress of Geologists, and now belongs 
to the Geographical Society of Berlin, runs as follows, ‘‘On trouve 
les valeurs actuelles des observations indiquées pres des stations 
par les mémes coulers que les coleurs correspondantes. Les observa- 
tions sur la declinaison seulement sont réduites en moyenne diurne.” 
Before publishing my pamphlet on magnetism I wrote to Sekino 
asking him to give me the exact times at which each observation 
was taken, and he replied that the values in the list I kept 
were daily means. I am certain that before leaving Japan I gave 
instructions for a reduction of all declinations to be made, and 
hitherto I was convinced that this had been done, although the 
reduction for the northern stations could only be approximate. If 
Dr. Knott has any doubts about the matter, he may readily remove 
them by inspecting Sekino’s field books, for, as stated above, these 
books were not written to be buried in the Archives of the Geological 
Survey, but were prepared for the use of future observers. 
There are, I think, very few persons who have a good idea of 
the surface configuration of the earth, even where only a small part 
is concerned. In most cases heights are exaggerated in memory, and 
consequently the angles of inclination are taken far too great. How 
insignificant is the depth of the deepest part of the ocean when 
compared with the dimensions of the globe as a whole! Lamont 
has tested the question as to whether there is any change in the 
magnetic elements due to differences of level, and the results show 
the change to be imperceptible even for considerable differences of 
height. From this he concluded that the seat of terrestrial magnetism 
is not to be sought near the surface, but at enormous depths below 
the surface. 
I may here be allowed to draw attention to a most interesting 
theory of Lamont. He admitted the frequent occurrence of irregu- 
larities in the systems of magnetic curves, and attributed them, not 
to the influence of magnetic masses contained in the crust, but to 
elevations and depressions, i.e. to irregularities, of the earth’s nucleus. 
His opinion may best be stated in his own words: “'The magnetic 
curves represent the surface of the nucleus.” If Dr. Knott had 
been well acquainted with these remote but classical investigations, 
he might have omitted the discussion of results given on page 214 
of his Memoir. 
In my pamphlet on Magnetism I have given a fairly complete 
