354 L. Page — A Century's Progress in Physics. 



A number of individuals kept systematic records of 

 meteorological observations, among whom was Loomis, 

 whose storm analyses did much to settle the merits of the 

 rival theories of Redfield and Espy. In studying the 

 storm of 1836 (40, 34, 1841) he had drawn on the map 

 lines through those points in the track of the storm where 

 the barometer, at* any given hour, is lowest. While this 

 method revealed the general direction in which the storm 

 was progressing, it failed to give much indication of its 

 size or shape. In discussing the two tornadoes of Feb- 

 ruary, 1842, one of which had already been described 

 in this Journal (43, 278, 1842), he adopted a new and 

 more illuminating graphical method. Instead of connect- 

 ing points of lowest pressure, he drew a curve through all 

 points where the barometer stood at its normal level, then 

 one through those points at which the pressure was 2/10 

 of an inch below normal, and so on. Temperature he 

 treated in much the same way, and the strength and 

 direction of the wind were indicated by arrows. This 

 innovation gave to his storm analyses a significance 

 which had been entirely lacking in those of his predeces- 

 sors, and led to the familiar systems of isobars and iso- 

 therms in use on the daily charts issued by the Weather 

 Bureau at the present time. Loomis advocated careful 

 observations for one year at stations 50 miles apart all 

 over the United States, so that sufficient data might be 

 obtained to settle once for all the law of storms. His 

 efforts, seconded by those of Henry, Bache, Pierce, Abbe, 

 and Lapham, led eventually to the establishment of the 

 Signal Service, and the publication of daily weather 

 maps according to the plan advocated thirty years 

 before. These maps afforded a basis for further 

 analyses of storms, which he published in numerous 

 "Contributions to Meteorology" (8, 1, 1874, et seq.) 

 between 1874 and his death in 1890. 



In addition to his work on storms, Loomis made a care- 

 ful study of the earth's magnetism (34, 290, 1838 et seq.), 

 and of the aurora borealis (28, 385, 1859 et seq.). That 

 a connection existed between sunspots, aurora, and ter- 

 restrial magnetism was already recognized. Loomis (50, 

 153, 1870 et seq.), however, snowed that the periodicity 

 of the aurora borealis, as well as of excessive disturb- 

 ances in the earth's magnetic field, corresponds very 

 closely with that of sunspots. 



