A410 J. D. Dana on some modern Calcareous Rock-formations. 
primary, or its period, or some circumstance by which it may be 
distinguished from the other satellites. 'The common sense of 
mankind has decided that in cities which are regularly laid out, 
it is much more convenient to designate the streets by numerals 
than by specific names. The only objection which is known to 
have been urged against applying the same system to the satellites 
is that the order is liable at any time to be changed by the dis- 
covery of new satellites. The history of the satellites has not 
shown this objection to be of a very serious nature. ‘The num- 
bering employed in any work must always be understood to be 
that which was true at the time the work was written. Any | 
supposed ambiguity arising from the use of letters of the alpha- 
bet or of numerals may be avoided by specifying (once for all) 
the approximate period of the satellite. Thus if we wished to 
refer to the satellites of Uranus we might say, satellite C (period 
8 days); or satellite D (period 13 days). Such a reference would 
be perfectly unambiguous, and would be much more readily com- 
prehended by the uninitiated than the formidable names of Titania 
and Oberon. 
It appears then that the periods of four of the satellites of 
Uranus have been pretty accurately determined; and there is 
strong reason to believe in the existence of two others whose pe- 
riods are about 37 and 92 days. It is quite possible that other 
satellites may exist, but we have no satisfactory data for forming 
even a probable estimate of their times of revolution. ‘The plane 
Uranus is now approaching the position most favorable for obser- 
vations in the Northern hemisphere, having at present a north 
declination of 13°, which will continue to increase until 1866. 
The orbits of the satellites also, which in 1840 appeared as straight 
lines, now appear as ellipses of moderate eccentricity, and will 
soon become sensibly circular. We anticipate that this period will 
be marked by the confirmation of Herschel’s observations of at 
least two additional satellites. 
en} 
Anr. XX XIX.—On some modern Calcareous Rock-formations ; 
by James D. Dana. 
In the last number of this Journal,* Prof. Horsford has pre- 
sented his views on the consolidation of the coral rocks of the 
Florida Reefs, and on the sources of lime in the growth of corals. 
As this author has shown some misconception of facts stated 8Y 
the writer,t and is somewhat in error in his chemistry, it appears 
CRE EAP EO 
* Page 245 of this volume; from the Proc. Amer. Assoc., vi, (Albany meeting,) 
207 and 412. 
_} The writer’s observations will be found in his Geol. Rep. Exp: Exped. Chap. 
TH, cited in this Journal, [2], xi, 357, xii, 25, 165, 329, xiii, 34, 185, 338, xiv, 76. 
, 
