A MEMOIR OP ELIAS LOOMIS. 745 



years later he published additional observations and a revised edition 

 of this map. 



These were the first published magnetic charts of the United States, 

 and though the materials for their construction were not numerous, aud 

 in many cases those obtainable were not entirely trustworthy, yet IC 

 years later, when a map was made by the United States Coast Survey 

 from later and more numerous data, Professor Bache declared tbat be- 

 tween his own now map and that of Professor Loomis, when proper 

 allowance had been made for the secular changes, the '' agreement tvas 

 remarl{ahleP 



The northern end of a ])erfectly balanced magnetic needle turns down- 

 ward, and the angle it makes with the horizon is called the magnetic 

 dip. This angle is an important one, and is obsi^rved with accuracy 

 only by using an expensive instrument, and taking unusual pains in 

 observing. Hence only a few observations of this element were found 

 by Professor Loomis. From these however he ventured to put on his 

 first magnetic map a few lines that exhibited the amount of the dip. 



While he was in Europe h< purchased a first-class dipping needle for 

 Western Eeserve College, and at Hudson and the neighborhood in term 

 time, aud at other places in vacation, he made observations with tbis 

 needle. Some of these observations were made before his second mag- 

 netic chart Avas published, and upon this map were now given tolerably 

 good positions of the lines of equal magnetic dip. But he continued 

 his observations for several years, determining the dip at over seventy 

 stations, spread over thirteen States, each determination being the mean 

 of from IGO to over 4,000 readings. These observations were published 

 in several successive papers in the transactions of the American Phil- 

 osophical Society at Philadelphia. 



Various papers on terrestrial magnetism, in continuation of his earlier 

 investigations, appeared in 1842, in 1844, in 1847, and in 1859, but 

 movements in Germany, England, and Russia had meanwhile been 

 inaugurated, which led to the establishment bj governments of a score 

 of well-equipped magnetic observatories, and this subject passed largely 

 out of private hands. 



Closely connected with terrestrial magnetism, and to be considered 

 with it, is the aurora borealis. In the week that covered the end of 

 August and the beginning of September, 1859, there occurred an exceed- 

 ingly brilliant display of the northern lights. Believing that an exhaust- 

 ive discussion of a single aurora promised to do more for the promo- 

 tion of science than an impeifect study of an indefinite number of them, 

 Professor Loomis undertook at once to collect and to collate accounts 

 of this display. A large number of such accounts were secured from 

 North America, from Europe, from Asia, and from places in tlie South- 

 ern Hemisphere ; especially all the reports from the Smithsonian observ- 

 ers and correspondents were placed in his hands by the secretary, 

 Professor Henry. 



