730 



SCIENCE. 



[N. S. Vol. IX. No. 230. 



restrial Magnetism, the Paris Academy 

 awarded him last year the Wilde prize of 

 four thousand francs, which was personally 

 presented by the President of the United 

 States. This honor is especially cqrrojMS 

 and particularly welcome to the friends of 

 science in this country, inasmuch as Mr. 

 Schott has just rounded out fifty years of 

 magnificent work in the Survey. 



With the addition of the islands of the 

 Atlantic and of the Pacific which have come 

 to the United States in the last year, and 

 with the need for investigation of general 

 laws of Terrestrial Magnetism for the whole 

 globe, it seems that the time has now come 

 for systematic magnetic operations, not only 

 upon the continent of North America, but 

 also on the islands in its vicinage. Witli 

 the purpose of carrying forward such a 

 magnetic survey and of completing in a rea- 

 sonable time the collection of such data as 

 may be necessary for a partial discussion of 

 the problems of the Magnetic Field of the 

 Earth, a new Division has been organized 

 in the office of the Coast and Geodetic Sur- 

 vey, known as the Division of TeiTCstrial 

 Magnetism. Dr. L. A. Bauer, formerly 

 assistant professor of mathematics and 

 mathematical physics at the University of 

 Cincinnati, and editor of the Journal of 

 lerrestrial Magnetism has been called to take 

 charge of this new division of magnetic 

 work. 



The following general plan of work, which 

 has been outlined as the basis for the mag- 

 netic survey of the United States and its 

 adjacent islands may be of interest. 



To indicate completely the laws which 

 hold in the Magnetic Field of the earth, it 

 would be desirable to have simultaneous 

 observations at a vast number of stations 

 over the continent of North America and 

 of the adjacent islands. This is, of course, 

 impossible, and the magnetic survey which 

 must be made will necessarily depend on 

 observations made at different times and 



reduced as accurately as possible to some 

 mean epoch. To arrive at a first prelimi- 

 nary result, it will probably be necessary to 

 make a general magnetic survey of the 

 country, observing the magnetic elements 

 at stations thirty or forty miles apart, makr 

 ing these stations more frequent in dis- 

 turbed areas if necessary. The secular va- 

 riations will necessarily be determined by 

 repeating the observations at representative 

 stations as the work goes on. The areas of 

 the countries at present belonging to the 

 United States are approximately as fol- 

 lows : 



United States, 3,025,600 square miles, 



Alaska, 577,390 " " 



Hawaiian Islands, 6,250 " " 



Puerto Rico, 3,5.30 " 



3,612,770 



This area is nearly equal to that of all 

 Europe and is one-fifteenth of the entire 

 area of the globe. As magnetic surveys 

 have been most vigorously prosecuted in 

 Europe, it will be of interest to note the 

 density of distribution of the magnetic sta- 

 tions in two recent, fruitful magnetic sur- 

 veys, viz., that of Great Britain, where 

 there was one station to every 139 square 

 miles, and that of Holland, embracing one 

 station to every 40 square miles. 



Suppose we were to decide upon one sta- 

 tion, on the average, to every 100 square 

 miles — an end that we must hope to attain 

 some day — then we should require the de- 

 termination of the magnetic elements at 

 30,000 stations within the United States. 

 At the rate of 400 stations a year, the mag- 

 netic survey, as detailed as this, would re- 

 quire for its completion 75 years. It is not 

 well, however, to have a magnetic survey 

 extend over such a long interval of years. 

 The errors incurred in reducing the obser- 

 vations to a common epoch would greatly 

 exceed the errors of observation. 



It is evident that we must either have a 

 very large number of observers and instru- 



