544 Dr. E. Naumann—WMagnetism and Earth Structure. 
his survey observations were taken at 80 stations, and in the first 
survey 200 stations were selected. When compared with the 
requirements of a detailed scheme, both these numbers appear very 
modest. In such cases it is all the more necessary to distribute the 
stations judiciously instead of merely spreading them “fairly over 
the whole country,” for it is only exhaustive surveys which can 
adopt the latter principle advocated by Dr. Knott. Similar remarks 
may apply in orographic surveys, for a reconnaissance requires quite 
a different distribution of stations to that needed for an elaborate 
undertaking in which time and money are not important. Having 
had some experience in reconnaissance surveying, I am well aware 
how carefully the stations must be selected. 
The above numbers also give us an idea how very far we still are 
from having accomplished detailed magnetic surveys even of parts 
of the earth’s surface; it is only in a few very limited districts in 
Missouri, Transylvania and Wuirtemberg that such surveys have 
been attempted. The whole question needs to be taken up inter- 
nationally, and I trust that these lines may convince my readers of 
the great importance of the subject. Rich harvests may be expected 
from a field which can only be explored by the joint efforts of all 
the workers in this great cause, and the stimulus imparted by British 
scientists will be sure to find a ready response on the continent. 
To many sciences the problem of terrestrial magnetism is the 
common focus, for physicists, geographers, topographers, meteorolo- 
gists, astronomers, etc., and above all geologists, must be interested 
in it. In former times magnetic observations were commonly 
attached to astronomical ones, and astronomers were in charge of 
the observations, whilst at present the subject forms a branch of 
physiography, and the observatories are usually connected with 
meteorological establishments. The latter arrangement seems to be 
the most satisfactory one, and great interest is taken in the question 
by meteorological societies and offices on the continent, particularly 
at Hamburg, Berlin, Vienna and Munich. 
To come to the practical side of the question, I beg to propose 
that an International Congress be held, say in London, at or about 
the time of the next British Association meeting. This Congress 
might decide numerous questions, still unsettled in the minds of the 
majority of observers, and may pass resolutions prescribing uniform 
schemes on which magnetic surveys should be carried out. It 
should also endeavour to induce the various Governments to take 
an active part in promoting the magnetic survey of their respective 
countries. 
Dr. Naumann’s paper is illustrated by Plates XV.—XIX. 
Plate XV. Locke’s Magnetic Sections; Palisades of the Hudson and Patterson, 
New Jersey. 
Plate XVI. Magnetic Curves of the Himalayas. 
Plate XVII. Tectonic Map of Japan with Dr. Knott’s Magnetic Curves. 
Plate XVIII. Comparative Diagram of Mr. Sekino’s and Dr. Knott’s Magnetic 
Curves of Japan. 
Plate XIX. Magnetic Tectonic Chart of Japan by Dr. KE. Naumann. 
