1819.] Proceedings of Philosophical Societies. 305 
of the mode of formation of the tube which Mr. Smith has first 
pointed out. The tube he has found to be completely external, 
and formed by a deep longitudinal depression in the surface of 
the pulp, which is destined to become the tooth. When the 
pulp is converted into tooth, the edges of it come gradually into. 
contact, and thus convert the depression into a tube. This tube 
is not lined with enamel, and in the common viper to the two 
sides of the tooth are cemented together by the enamel, which 
thus constitute the sutor of the tooth. 
XII. On the Parallax of « Aquile. By John Pond, Esq. 
F.R.S. Astronomer Royal.—From a set of observations made 
with the telescope, erected for the express purpose of observing 
this star, in which it was compared with / Pegasi, Mr. Pond 
considers himself entitled to conclude, that it exhibits no 
evidence whatever of having a parallax. 
XIII. On the Parallax of the fired Stars in right Ascension. 
By John Pond, Esq. F.R.S. Astronomer Royal.—The observa-+ 
tions contained in this paper coincide with those formerly made 
by Mr. Pond, in showmg that the parallax of the brightest stars 
cannot possibly exceed half a second, and that it is very unlikely 
that it should amount to half that quantity. 
’ XIV. An Abstract of the Results deduced from the Measure- 
ment of an Arc of the Meridian, extending from Lat. 8° 9’ 38:4” 
to Lat. 18° 3’ 23-6” N. being an Amplitude 9° 53’ 45°2”. By 
Lieut.-Col. Wiliam Lambton, F.R.S. 33d regiment of foot.— 
Some account of the results of this interesting measurement was 
given in the last number of the Annals of Philosophy. Col. 
Lambton is in hopes that the measurement of the arc will be 
continued still further north, and that at some future period it 
may be extended even as far north as Delhi. 
Articte VIII. 
Proceedings of Philosophical Societies: 
ROYAL SOCIETY. 
Feb. 25.—A paper, by Sir H. Davy, was read, on the forma- 
tion of mists in particular situations. The author commenced 
by observing, that the fall of temperature after sun-set is greater 
on land than on water; and referred to the well-known peculia- 
rity in the expansibility of water at temperatures below 40°, as 
the cause by which both the water and the superincumbent air 
are preserved at a superior temperature. When, therefore, 
according to Sir H. Davy, the cold and comparatively dry land 
air mixes with the warmer and moister air resting upon the 
water, the diminution of the temperature of the latter occa- 
sioned by this mixture has a tendency to separate a portion of 
its moisture in the form of mist. 
Vou. XIII, N°1V. U 
