378 Proceedings of Scientific Societies. 
Dr. Horner alludes to the erroneous nature of the early ideas of natu- 
ralists on the teeth of the mastodon, and observes that we now know, with 
some degree of certainty, that the earliest teeth of this animal were not 
more than an inch and a half square, and that the three immediately suc- 
ceeding were a gradual and successive enlargement on this and on each 
other’s volume. In the museum of Mr. Koch, at St. Louis, there is a 
young head, the long diameter of which is 18 or 20 inches, where the fact 
of four co-existent teeth on each side of each jaw is exhibited. This spe- 
cimen, with a dozen lower jaws of different ages and sizes, enables us to 
trace, with some accuracy, the stages of dentition, until it reaches the 
large and solitary grinder of ten inches in length on each side. Judging 
from these phases of dentition, Dr. Horner infers that the entire amount 
of teeth was at least 24; he is disposed, indeed, to think that the number 
may have been greater than this; perhaps 28, and possibly 32. 
Dr. Horner makes some observations on some specimens of lower jaws 
in Mr. Koch’s museum in St. Louis, in which there was a solitary tusk on 
the right side, and alludes to the embarrassments that their existence oc- 
casions in regard to the Tetracaulodon of Godman ; whether, for example, 
we are to consider them merely as abnormous types of that animal, as 
known mastodons, or as still another species to which, if such, the name 
Tetracaulodon 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 
atusk, 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 alve- 
olus on the right. 
It is very far from being certain, Dr. Horner adds, that any example 
exists of the upper jaw of the Tetracaulodon ; the presence of tusks in both 
jaws at once has therefore to be yet proved. 
he committee consisting of Prof. Bache, Dr. Patterson, and Mr. Lu- 
kens, to whom was referred the paper, entitled ‘observations to deter- 
mine the magnetic intensity at several places in the United States, with 
some additional observations of the magnetic dip, by Elias Loomis, pro- 
fessor of mathematics and natural philosophy in Western Reserve Col- 
lege,” recommended the same for publication in the Society’s Transac- 
tions, which was ordered accordingly. 
The following is an abstract of the results of observations contained in 
is memoir. 
1, Magnetic Intensity—The horizontal intensity was observed by an 
apparatus similar to the one used by Prof. Hansteen. Three small nee- 
dies furnished to the author by Prof. Renwick, and made under the direc- 
tion, respectively, of Professor Hansteen, Major Sabine, and Prof. Henry, 
were employed. The commencing semi-arc of vibration was, in every 
