2S-I 



Magnetic Observations. 



call magnets, or those bodies susceptible to magnetism; and, by ob- 

 serving the varying movements of these bodies — suspended or other- 

 wise so placed as to be free to the magnetic influence — we write down 

 these movements, record the changes of pointing, trace the curves of 

 motion, and find the intensity; until, by thus watching bodies controlled 

 by the magnetic influence, we form some opinion of the invisible force 

 that occasions these movements. Thus, with the aid of the various 

 forms of magnetometer, we obtain mental concepts; ideals of the 

 geometry of magnetic lines in space which, when systematized, may 

 enable us, from a knowledge of the past events in terrestrial mag- 

 netism, to make predictions of future occurrences that will be of 

 great benefit to mankind. 



If for the theoretical " Ether" of school philosophies we substitute 

 the idea of a ubiquitous multi-mode energy; ever existent in some 

 ratio to matter, however infinitesimally attenuated this matter may 

 be; we conceive an energy capable of an infinite variety of reactions, 

 in accordance with the position or form of matter affected by it, and 

 by this idea may arrive at a better conception of the nature of the phe- 

 nomena of magnetism. Nor is this the only useful result of this 

 modification of theory; for this conception of the energy of space, if it 

 agree more closely and rationally with the facts of nature, may also, 

 perhaps, account for all the so-called "physical forces/' as resultants 

 of the reactions of the diffused energy of space on the various local as- 

 pects of energy and matter. 



It is not the purpose of the present paper, however, to consider or 

 investigate the existence of a primal form of energy which shall re- 

 place in physical theory the "Ether" of the speculative philosophers. 

 My views on this subject are already before the Institute. 



The object of the present paper is to make public some new local 

 magnetic data, with notices of other and more ancient records, which 

 have hitherto escaped notice. It is thought best to accompany these 

 observations with some calculations, which I have made by the 

 formula considered by the chief mathematician of the United States 

 Coast Survey the closest approximation so far made to the law of the 

 magnetic declination at Albany, as a means of predicting the positions 

 of the compass needle through its secular movement for many years to 

 come. By comparing the computed predictions with the actual variation 

 observed, not only is an idea had of the accuracy of this method of pre- 

 diction — and, vice versa, of the irregularities in the actual movement of 

 the needle as observed — but some notion also will be had of what is 

 being sought by students of terrestrial magnetism, while the column of 



