E ro 
346 Professors W. B. and R. BE. Rogers 
to the diminution =1,%, inches; or for the sexagesimal Siete 
. = 0°000077 mile =A an inches. 
These minute quantities are insufficient to account for the ge- 
ological evidences of the diminished diameter of the globe, in- 
ferred from facts stated in the work alluded to, unless the period 
of time be regarded as almost infinite, but it is believed thata 
- clue is perceived, by which compensating forces would maintain 
the time of rotation nearly uniform, and the day of nearly an 
invariable length, even if the earth be either gradually or par- 
oxysmally undergoing a slight change in its dimensions. 
Ohio University, Athens, Dec. 9th, 1843. 
po XVIIL—An Account of some new Instruments and Pro: 
cesses for the Analysis of the Carbonates; by Profs. Wi.ttaM 
B. Rocrers and Roser E. Rocers, of the Univ. of Virginia. 
Tue importance of some ready means of determining the com- 
: position of the calcareous and other carbonates, so extensively 
used in agriculture and the chemical arts, and the frequent neces 
sity of such analyses in the course of chemical research, have 
suggested various forms of apparatus and modes of proceeding 
adapted to this purpose, Of these the most generally used are— 
first, that of Rose, as described in his Chemlcal Analysis, in which 
the quantity of carbonate present is determined from the weight 
of the carbonic acid expelled; secondly, that of mingling the 
carbonate and hydrochloric acid in a graduated tube over mét- 
cury, and estimating the amount of the pure carbonate from the 
volume of carbonic acid which collects in the tube ; and thirdly, 
that of adding to the carbonate an acid of known she ength, until 
neutralization is effected, and computing the amount of carbonate 
from the quantity of ceil used. T'o these may be added, the 
modifications of Rose’s apparatus employed by Fritche, and by 
Erdman and Marchand ; the very neat process of Dr. J. L. Smith, 
described in this Sainnal Vol. xiv, p. 262, which is an application 
of the last of the three methods above mentioned ; and the ing 
nious but cumbrous, and we think inexact, iaaimnent recently 
proposed by Drs. Will and Fresenius.* 
eee aS 
| * We may also add the method recently proposed by M. pohargnee es (Pogge? 
dorff, Ann. der Phys. und Chem. 1842,) which is as follows. In a platina erucible 
holding about 18 grammes of water, are placed from 2 to 7 grammes of glass © a 
