British Association; but as he proposed to deal with the entire disc in this way, the magnitude and ambitious character of the scheme soon damped the ardour of those who at first supported it, and it was ultimately abandoned.  It was, however, based on the only feasible principle which, as it seems to the writer, will not result in doubt and confusion.  Now that photography has come to the assistance of the observer, Mr. Birt’s proposal, if confined within narrower limits, would be far less arduous an undertaking than before, and might be easily carried out.  A complete photographic survey of a few selected regions, as a basis for an equally thorough and exhaustive scrutiny by direct observation, would, it is believed, lead to a much more satisfactory and hopeful method for ultimately furnishing irrefragable testimony as to permanency or change than any that has yet been undertaken.

CATALOGUE OF LUNAR FORMATIONS

FIRST QUADRANT

WEST LONGITUDE 90 deg.  TO 60 deg.

SCHUBERT.—­This ring-plain, about 46 miles in diameter, situated on the
N.E. side of the Mare Smythii, is too near the limb to be well observed.

NEPER.—­Though still nearer the limb, this walled-plain, 74 miles in diameter, is a much more conspicuous object.  It has a lofty border and a prominent central mountain, the highest portion of a range of hills which traverses the interior from N. to S.

APOLLONIUS.—­A ring-plain, 30 miles in diameter, standing in the mountainous region S. of the Mare Crisium.  There is a large crater on the S.W. wall, and another, somewhat smaller, adjoining it on the N. There are many brilliant craters in the vicinity.

FIRMICUS.—­A somewhat larger, more regular, but, in other respects, very similar ring-plain, N.W. of the last.  Some distance on the W., Madler noted a number of dark-grey streaks which apparently undergo periodical changes, suggestive of something akin to vegetation.  They are situated near a prominent mountain situated in a level region.

AZOUT.—­A small ring-plain, connected with the last by a lofty ridge.  It is the apparent centre of many other ridges and valleys which radiate from it towards the N.W. and the Mare Crisium.  There is a central mountain, not an easy telescopic object, on its dusky floor.

CONDORCET.—­A very prominent ring-plain, 45 miles in diameter, situated on the mountainous S.W. margin of the Mare Crisium.  It is encircled by a lofty wall about 8000 feet in height.  The dark interior of this and of the three preceding formations render them easily traceable under a high angle of illumination.

HANSEN.—­A ring-plain, 32 miles in diameter, on the W. border of the Mare Crisium N. of Condorcet.  Schmidt shows a central mountain and a terraced wall.

ALHAZEN.—­This ring-plain, rather smaller than the last, is the most northerly of the linear chain of formations, associated with the highlands bordering the S.W. and the W. flanks of the Mare Crisium.  It has a central mountain and other minor elevations on the floor.  There is a little ring between Alhazen and Hansen, never very conspicuous in the telescope, which is plainly traceable in good photographs.