284 Proceedings of Societies. 
oferror. The other electrical measurements in the absolute system offer 
comparatively little difficulty. 
‘** Researches on the Moon.” By Prof. Pariturrs.—The author having 
on previous occasions presented his views as to the methods and objects 
of research in the moon, was desirous now to state a few results, and ex- 
hibit a few drawings, the fruit of recent examinations of the moon by 
means of a new equatorial by Cooke, with an object-glass of 6 inches. 
In sketching ring mountains, such as Theophilus and Posidonius, the 
author has been greatly interested by the changes of aspect which even a 
small alteration in the angles of elevation and azimuth respectively pro- 
duce in the shadow and lights. Taking an example from Cyrillus, with 
its rocky interior, and fixing attention on the nearly central mountain, it 
always appears in the morning light to have two principal unperforated 
masses. By a slight change in the direction of the light, the division of 
these masses is deeply shaded on the north or deeply shaded on the south, 
and the figure of the masses, 7.e. the limit of light and shade, seems 
altered. A slight change in the angle of elevation of the incident light 
makes more remarkable differences. On Posidonius, which is a low, 
nearly level plateau, within moderately raised borders, the mid-morning 
light shows with beautiful distinctness the shield-like disc of the moun- 
tain, with narrow broken walls, and in the interior, broad, easy undu- 
lations, one large and several smaller craters. In earlier morning more 
craters appear, and the interior ridges gather to form a broken terrace 
subordinate to the principal ridge. This cireumstance of an interior 
broken terrace, under the high main ring of mountain, is very frequent, — 
but it is often concealed by the shadow of the great ridge in early morning 
shadows. ‘To see it emerge into half-lights, and finally to distinct digita- 
tions and variously directed ridges, as the light falls at increasing angles, 
is a very beautiful sight. But it is chiefly to the variations in the central 
masses of lunar mountains and their physical bearings that the author 
wishes to direct attention. Many smaller mountains are simply like cups 
set in saucers, while others contain only one central or several dispersed 
cups. In Plato is a nearly central very small cup, bright, and giving a 
distinct shadow on the grey ground, as seen by Mr Lockyer, Mr Birt, and 
Professor Phillips himself. But in the centre of many of the larger moun- 
tains, as Copernicus, Gassendi and Theophilus, is a large mass of broken 
rocky country, 5,000 or 6,000 feet high, with buttresses passing off into 
collateral ridges, or an undulated surface of low ridges and hollows. The 
most remarkable object of this kind which the author has yet observed with 
attention is in Theophilus, of which mountain two drawings are given, 
in which the author places equal confidence, except that the later drawing 
may have the advantage of more experience. ‘The central mass is seen 
under powers of 200-400 (the best performance is from 200 to 300), and 
appears as a large conical mass of rocks about fifteen miles in diameter, 
and divided by deep chasms radiating from the centre. The rock-masses 
between these deep clefts are bright and shining, the clefts widen towards 
the centre, the eastern side is more diversified than the western, and like 
the southern side has long excurrent buttresses. As the light grows on 
the mountain, point after point of the mass on the eastern side comes out 
of the shade, and the whole figure resembles an uplifted mass which broke 
with radiating cracks in the act of elevation. Hxcepting in steepness, 
this resembles the theoretical Mont d’Or of De Beaumont ; and as there 
is no mark of cups or craters in this mass of broken ground the author is 
disposed to regard its origin as really due to the displacement of a solidi- 
fied part of the moon’s crust. He might be justified by Prof. Secchi’s 
drawing of Copernicus, in inquiring if the low excurrent buttresses may 
