308 



to which, if such, the name Tetracauledon might be attached. Dr. 

 Horner confesses himself unable to suggest a probable solution of these 

 questions, and states, in connection with them, that Mr. Koch has the 

 lower part of the head of a Mastodon of middling size, in which, from 

 the intermaxillary bone, as usual, protrudes a tusk, which measures 

 thirty inches long by four inches in diameter; but the tusk exists 

 only on the left side, there being not even a vestige of alveolus on 

 the right. 



It is very far from being certain, Dr. Horner adds, that any exam- 

 ple exists of the upper jaw of the Tetracauledon; the presence of 

 tusks in both jaws at once has therefore to be yet proved. 



The Committee, consisting of Prof. Bache, Dr. Patterson, 

 and Mr. Lukens, to whom was referred the paper, entitled 

 "Observations to determine the Magnetic Intensity at several 

 Places in the United States, with some additional Observations 

 of the Magnetic Dip, by Elias Loomis, Professor of Mathe- 

 matics and Natural Philosophy in Western Reserve College," 

 recommended the same for publication in the Society's Trans- 

 actions, which was ordered accordingly. 



The following is an abstract of the results of observations contained 

 in this memoir. 



1. Magnetic Intensity. — The horizontal intensity was observed by 

 an apparatus similar to the one used by Professor Hansteen. Three 

 small needles furnished to the author by Professor Renwick, and 

 made under the direction, respectively, of Professor Hansteen, Major 

 Sabine, and Professor Henry, were employed. The commencing 

 semi-arc of vibration was, in every case, 30°, and each series in- 

 cluded 320 oscillations, the instant of the completion of every tenth 

 vibration being noted. No correction, therefore, is applied for the 

 arc of vibration. The times were observed at Dorchester, Princeton, 

 and Philadelphia, by a chronometer, and at the other stations by a 

 lever watch, which, at Hudson, was compared with the observatory 

 clock before and after the observations. The author remarks, that 

 " at the remaining stations there is a little uncertainty with regard to 

 the time, yet it is thought its influence upon the results will not be 

 great." 



The correction for temperature, for each of the needles, was ob- 

 tained by direct experiment, and gave the following coefficients : — 



