National Geographic : 1899 Aug
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 TerrestrialMagnetism 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 under the Jurisdictionof 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. 467-470.