JANUABT 13, 1911] 



SCIENCE 



53 



A BROAD VIEW 



I began my address by setting before you 

 some of the results of research in a field 

 which I am ready to acknowledge appears, 

 as I have already said, a very restricted 

 and special one. But as we progress we 

 are continually forced to raise questions 

 which go far beyond our specialty and 

 touch at the very heart of matters in which 

 we all take a common and lively interest. 



The all-comprehensiveness of terrestrial 

 magnetic phenomena makes us more than 

 ever aware of the necessity of taking broad 

 views and keeping our minds ever open 

 and free so that we may receive and weigh 

 the facts observed with the proper care 

 and in the proper scientific spirit. 



The terrestrial magnetician is continu- 

 ally having forced upon him the fact that 

 the "axis of the universe does not stick out 

 of his own back yard. ' ' He can not follow 

 the example of his more fortunate brother, 

 the geodesist, who, from careful measure- 

 ments made over but a very limited por- 

 tion of the earth can determine its figure 

 with wonderful precision, the best possible 

 demonstration of which we shall have to- 

 day from the address of the retiring chair- 

 man of Section D. To the geodesist a mass 

 of lead is the same as an equal mass of 

 magnetic iron ore; not so, however, to the 

 magnetician. Were he to attempt the de- 

 termination of the position of the earth's 

 magnetic axis and of the earth's magnetic 

 moment from a series of extensive mag- 

 netic observations in the United States, he 

 would obtain results totally different from 

 those similarly derived for an area of equal 

 size in some other part of the globe. So 

 likewise, as we have found with respect to 

 the earth's magnetic disturbances, five 

 well distributed magnetic observatories can 

 accomplish more, viewed from a general, 

 terrestrial standpoint, than twenty of the 

 best equipped magnetic observatories con- 



centrated in but a limited portion of the 

 earth, however civilized that portion may 

 be. 



Thus the student of magnetism has 

 difficulties not encountered in geodesy, and 

 he would appear to suffer under great dis- 

 advantages. Perhaps, however, the disad- 

 vantages under which he labors as regards 

 one object may become a source of advan- 

 tage in a totally different one; by the 

 very f.aet that to the magnetician a lump 

 of iron is different from a similar mass of 

 lead he is enabled to draw certain conclu- 

 sions with regard to the materials forming 

 the earth, denied to the geodesist. One of 

 our foremost geologists has predicted that 

 our knowledge of the internal constitution 

 of the earth is to be advanced primarily 

 through terrestrial magnetism and seismol- 

 ogy. 



Beginning with Gauss and up to within 

 comparatively a few years ago, it was be- 

 lieved that it would be possible to establish 

 a mathematical expression having a lim- 

 ited number of coefficients which would rep- 

 resent the magnetic observations made over 

 the earth's surface, if not entirely within 

 an error of observation, certainly within 

 an error of approximately the same order. 

 However, as carefully conducted mag- 

 netic surveys become more extensive, it 

 is becoming more and more evident that it 

 is useless, for practical purposes, to estab- 

 lish such mathematical formulas. Were 

 we, for example, to have magnetic data all 

 around the globe at intervals of five de- 

 grees in latitude and longitude, hence at 72 

 points on a parallel, it would be possible to 

 set up a formula which should represent 

 absolutely the values at the points given, but 

 even for this case the expression would in- 

 volve so many unknowns as to make the 

 computation practically prohibitive. And 

 after all this labor had been accomplished, 

 it would not be possible to obtain the mag- 



