TRANSACTIONS OF THE SECTIONS. 9 
orbits of the satellites, The satellites themselves he considered to have been 
formed from portions of matter left behind during the contraction into a globe of 
such a plane, which had at first occupied the whole space included within the pre- 
sent orbits of the satellites. This view of the formation of the satellites he based 
on the fact that the period of diurnal rotation in each of them corresponded with 
the period of its revolution round its primary, which he showed would be the case 
with any body whatever, if so left behind or lifted off a planet. 
The author then discussed the chemical changes that would ensue on the surface 
of the earth after it had assumed the globular form. Oxidization of its metallic 
constituents would absorb a vast proportion of its gaseous matter, and the forma- 
tion of water would remove a great deal in addition. Hence the absence of atmo- 
sphere or water on the moon’s surface might be accounted for, as she would carry 
oif with her only j;th portion of the gaseous elements of the planet, and her sur- 
face exposed to the chemical action of those elements would be much more than 
sth that of the earth. Water also might be quite absorbed on her surface in the 
formation of hydrates of the alkaline and earthy bases. 
On the earth, sodium would unite with chlorine, and common salt would result; 
and to the large amount of salt so formed the author ascribed the saltness of the 
ocean; rivers could only carry to the sea salt obtained from soil originally deposited 
by the ocean, and which must therefore have derived its salt from the sea. This 
rocess must be still going on, and hence Dr. Ashe inferred that the sea could never 
ave become salt, or be now increasing in saltness, from that cause; hence he dis- 
sented from that view, which was the one universally put forward by geologists, 
On a Group of Lunar Craters imperfectly represented in Lunar Maps. 
By W. R. Bret, FLAS. 
One of the objects of lunar maps should undoubtedly be such a representation of 
the forms of the irregularities of the moon’s surface, that a student may readily, at 
the switable epochs, ascertain the general outlines and configurations of the parts as hs 
he is studying, so as to be certain that he has not misapprehended either the position 
or form of any particular portion of the lunar surface. 
A map constructed for a given epoch, at the full for instance, that shall give those 
features by which every crater, mountain-chain, and plain may be instantly recog- 
nized, is at the present moment a desideratum. Indeed, on such a map some craters 
would not find place, A certain angle of illumination is necessary to bring out 
saliently the distinguishing features of a crater or mountain-chain; and a series of 
maps that would exhibit each to the best advantage, must include as many distinct 
epochs of illumination in their construction as there are meridians encircling the 
lunar globe. 
One of the greatest monuments of the skill and industry characterizing astrono- 
mical science is undoubtedly Beer and Méidler’s large map of the Moon. To the 
student of selenography it is invaluable; his progress would be slow without it. 
The writer of this paper cannot, however, agree with Crampton “that every 
mountain and every valley, every promontory and every defile on the moon’s 
surface, finds its representative on that map.” On the contrary, in his examination 
of the lunar surface, he has met with several instances of features not recorded 
thereon, a recent instance of which forms the subject of the present paper. 
In the neighbourhood of a fine chain of craters that come into sunlight from ten 
to thirteen days of the moon’s age, and are well seen under the evening illumination 
from twenty-one to twenty-four days of the moon’s age, lying in the northern regions 
of the moon from 57° to 74° N. Lat., and from 25° to 50° J E Long., and designated 
Philolaus, Anaximenes, and Anaximander, with an unnamed crater between Anaxi- 
menes and Anaximander, are three crater-form depressions, of which there are nume- 
rous examples on the moon’s surface,—the usual characteristics being, Ist, an 
extensive floor, exhibiting a variety of surface in different specimens, often pierced 
with small craters and diversified with hills; 2nd, a more or less perfect rampart, 
here and there pierced with craters, and rising into elevated peaks, so that the entire 
depression is readily recognized as a distinct formation, completely separated from 
its surrounding neighbours. Two such depressions, lying nearly in the same 
meridian, and connected by a table-land or plateau, are very imperfectly, if at all, 
