65 



mao-netical instruments will form a kind of ^'■mineral or divining 

 rod'' to the geologist. 



There was exhibited, also, a chart of the United States, showing, 

 chiefly, the isodynamic lines consistent with the observations. These 

 lines form ovals around Lake Superior as an axis, the longer or 

 pointed ends pointing towards New York, and in the opposite direc- 

 tion. The outer oval descending along the Hudson river, passing 

 through the city of New York, along the coast, to near Baltimore, 

 and, turning westward, traverses Maryland, Virginia, and Kentucky, 

 and crosses the Mississippi into Missouri about thirty miles below St. 

 Louis. 



The force along this line is 994, that at Cincinnati, in Ohio, being 

 1000 ; and an oval is delineated at every increase of 10, until, at the 

 axis at Lake Superior, it rises to from 1054 to 1060. But, Professor 

 Locke stated, more observations are needed to fix more precisely those 

 lines at remote points, and he expressed a desire, that the observa- 

 tions of Major Graham, Prof. Bache, and Prof. Loomis, together with 

 his own, might be united in a suitable chart, such as might be pro- 

 duced by a convention of observers. Two other charts, explained 

 in the communication, were also exhibited ; the one a copy of a part 

 of Col. Sabine's north polar chart, with additions, and with a delinea- 

 tion of the relative positions of the astronomical poles, the pole of 

 dip and convergence discovered by Ross, and the pole of intensity at 

 Lake Superior; and the other a particular delineation of Copper 

 Harbour and of Porter's Island, where, in Prof. L.'s line of observa- 

 tions, he found the greatest intensity of force. 



Dr. Dunglison read the follov^ing supplementary remarks 

 made by the late President to his last vs^ill and testament, in re- 

 lation to this Society, as well as to others. 



"Having thus disposed of my worldly property, I take the liberty to 

 recommend to my brethren of the bar the Law Academy of Philadel- 

 phia, that they may take it under their special protection, so as to 

 make it as useful as possible to the progress of our noble science. A 

 law professorship has long been wanted in this city : several of the 

 states have the advantage of us in this respect. I recommend this 

 important subject to the consideration of the friends of the legal 

 science, and who are desirous of making it redound more and more 

 to the honour of Pennsylvania. 



The Historical Society of Pennsylvania is in danger of perishing 



