Physiognomy of the Momis Surface. 39 



without his intending, however,'' to identify them with terres- 

 trial seas, but only because no better term of comparison oc- 

 curred to him. Subsequent observations have more and more 

 clearly demonstrated that these portions of the moon could not 

 be entirely covered by a liquid ; for they present inequalities 

 of different kinds, also a colour which is any thing but uniform, 

 and besides void hollows are seen, as their shadows demon- 

 strate. Hence, although we ought not from these to con- 

 clude in an absolute manner that there is neither water nor other 

 analogous fluid on the moon's surface, nothing more is to be un- 

 derstood by the word seas than certain extended and greyish 

 portions which appear somewhat lower, and comparatively 

 more uniform than the brighter parts by which they are sur- 

 rounded. 



On that hemisphere of the moon which is turned towards the 

 earth, there are only two seas, of moderate size, which are iso- 

 lated and bounded on all sides, viz. the Mare Crisium, and 

 the Mare Humorum. The larger ones, like the Mare Sere^ 

 nitatiSy are only partly defined : for not only are they con- 

 nected among themselves, as are the great oceans of our planet, 

 but they are often likewise devoid of any decided line of de- 

 markation, distinguishing them from the brighter regions. This 

 is particularly the case with the sea Mare Nubium, although 

 very near the centre of the moon, and with the Oceanus proceU 

 larum^ which is the largest within our view. At the same time, 

 a slight difference in lustre may be observed, between the con- 

 tiguous parts of these different surfaces when viewed as a whole. 



It may be stated in general terms, that the grey portions oc- 

 cupy nearly two-fifths of the visible surface of the moon. They 

 exist to the greatest extent in its eastern and northern portions, 

 and quite disappear in the most southerly part. Hevelius, as 

 already stated, gave them the names of terrestrial seas ; but 

 Riccioli shortly afterwards introduced another nomenclature, 

 which was founded upon the alleged influences of the moon up- 

 on terrestrial meteorological phenomena, and upon man's corpo- 

 real and mental condition ; and this system, notwithstanding 

 its absurdity, has been adopted. These names are now conse- 

 crated by the usage of more than two centuries, and they could 

 not be altered without introducing much confusion. 



