288 MAGNETIC WORK OF COAST AND GEODETIC SURVEY 



cial company's stations as a base of supplies and assistance, the 

 ascent of Makushin could be made direct from Unalaska, and 

 that volcano fully investigated in about three or four days. 



Dr Dall,* in his work- on Alaska, has presented a very inter- 

 esting and instructive chronological tabulation of the activities 

 of the volcanoes of Alaska, from which it would appear that 

 there has been great diminution of energy with the passage of 

 time. The systematic exploration and study of these volcanoes, 

 as well as the associated volcanic areas, are well worth the atten- 

 tion of geographic societies in America, or those who can com- 

 mand leisure and a little money ; but perhaps we shall have to 

 wait, as in the case of Mt St Elias, for another Prince Luigi to 

 come and tell us the facts concerning Shishaldin and Akutan. 



MAGNETIC WORK OF THE COAST AND GEODETIC 



SURVEY 



By L. A. Bauer, 

 Chief of Division of Terrestrial Magnetism 



From the date of the organization of the Coast Survey the 

 supplying of magnetic data to the land surveyor and the mariner 

 has formed one of the chief functions of its work. With every 

 year the demand for such data has become more and more press- 

 ing, so that the present superintendent, Dr Henry S. Pritchett, 

 has found it necessary to form a distinct division for magnetic 

 work. The work that it is proposed to carry Out with the en- 

 larged opportunities may be briefly classified as follows : 



1. Magnetic Survey of Land Areas imder the Jurisdiction of the 

 United States. The three elements, magnetic declination or 

 "variation of compass," magnetic inclination or dip, and the 

 intensity of the magnetic force, will be determined at stations on 

 the average 25 to 30 miles apart. As the endeavor will be to 

 observe at about 500 stations per annum, it is estimated that 

 the complete survey of the country will take about ten years. 

 The short-period variations, as the diurnal variation of the 

 magnetic declination, will be eliminated with the aid of the con- 

 tinuous observations at the magnetic observatories, while the 



* Dall (W. H.) : Alaska and its Resources, pp. 407-470. 



