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and was repelled from the wick, the ends being invariably re- 
versed’ in changing its course, I observe that having repeatedly 
examined other candles, I have not been able to discover any 
thing more than the ordinary capillary attraction in them; and 
am led to believe the repulsion in the case cited, was owing to an 
accidental evolution of minute bubbles of gas at the base of the 
exposed wick. I am strengthened in this opinion, by having ob- 
served some time ago a similar phenomenon in an ash-hopper 
-while in operation, in which the cause was obvious; the calm, 
supernatant water, appeared to be very gently directed to several 
little vertices, bearing thither fragments of coal, &c.; as soon as 
they reached ‘the center, a small bubble of air arose in that spot ; 
and bursting, caused the particles adjacent to wheel about and re- 
treat. . 
Tooth and Grinder of a Mastodon.—The grinder of a Mas- 
todon ?* and the tusk of an Elephant have been found in this 
State; the first sixteen, and the second thirty miles from this 
place. The tusk was disinterred from a bed of gravel: it must 
have been originally at least six feet in length. Both specimens 
are now in our “ Atheneum.” 
Arr. XVIIL.—On Terrestrial Magnetism ; by Joun Locke, 
M. D., Professor of Chemistry and Pharmacy in the Medical 
College of Ohio. 
Medical College of Ohio, Nov. 20, 1840. 
TO THE EDITORS. 
You are already apprised that there was an erratum in my last 
manuscript, published in Vol. xxx1x, p. 319, of this Journal, mak- 
ing an apparent disagreement in the results by the two dipping 
needles at Davenport, in Iowa, amounting to 6.75. As the object 
of that communication was to show that the separate results ob- 
* Dr, Plummer’s mark of interrogation, implies a doubt which we presume will 
be easily removed by an examination of the tooth; if of an elephant, it should 
have low y itl lt ling tl hould d vertically through 
from top to bottom ; if of the mastodon, the processes will be high and strong, ae 
the enamel only superficial over the entire tooth —Sen. Ep, 
