432 Professor Elias Loomis. 



Academy of Arts and Sciences for its sympathy and aid. The 

 work of collecting facts was so far advanced before leaving 

 New Haven that when he had been a few months Professor 

 at Hudson, he forwarded to the American Journal of Science 

 a discussion of the observations thns far obtained, and with 

 them a map of the United States, with the lines of equal 

 deviation of the needle drawn upon it. Two 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, and in many cases those obtainable were 

 not entirely trustworthy, yet sixteen years later, when a map 

 was made by the United States Coast Survey from later and 

 more numerous data, Professor Bache declared that between 

 his own new map and that of Professor Loomis, when proper 

 allowance had been made for the secular changes, the " agree- 

 ment was remarkable" 



The northern end of a perfectly balanced magnetic needle 

 turns .downward, and the angle it makes with the horizon is 

 called the magnetic dip. This angle is an important one, and is 

 observed 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 he purchased a first class dipping 

 needle, for Western Reserve College, and at Hudson and the 

 neighborhood in term time, and at other places in vacation, he 

 made observations with this needle. Some of these observa- 

 tions were made before his second magnetic chart was pub- 

 lished, 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 160 to over 4,000 readings. These 

 observations were published in several successive papers in the 

 transactions of the American Philosophical Society at Phila- 

 delphia. 



