46 
November 10th, 1868. 
A. Brothers, F.R.A.S., in the Chair. 
Mr. E. W. Binney, F.R.S., F.G.S., was elected President of 
the Section in place of Mr. Robert Worthington, F.R.A.S., 
deceased. 
“On the Lunar Spot IYAa 17, IYA£ 39,” by Joseph 
Baxendell, F.R.A.S. 
Since January last, when Mr. W. R. Birt, F.R.A.S., com- 
municated to this Society the observations made by the Rev. 
W. O. Williams, of Pwllheli, which had led him to regard 
the spot numbered 17 and 39 on the British Association Lunar 
Maps of areas IYAa and IYA£ as variable, I have occasionally 
examined this spot, but up to the present time I have 
observed no indications of change. On the night of the 
2nd of April, however, I noticed near to it, on the following 
or eastern side, a small crater which is not marked on the 
maps of the British Association, nor on any other published 
maps or drawings that I have yet seen. This crater was 
observed again on the nights of the 2nd and the 30th of 
May, when it was by no means a difficult object. I was 
therefore much surprised on looking over the series of 
observations given by Mr. Birt in his communication printed 
in the June number of the Monthly Notices, to find that 
none of the observers had noticed this crater. On the 27th 
of July I again observed it from 9h. 45m. to lOh. 15m., 
when it appeared as a small black spot, the interior being 
almost, if not quite, filled up with shadow, and I noted that 
it was on the outer slope of the boundary ridge of Hipparchus, 
while IYAa 17, XYA Z, 39 was on the inner slope. On this 
occasion I also observed that the outline of the shadow of 
the west wall of the crater, which Mr. Williams suspects to 
be variable, was very irregular in form, indicating conside- 
rable differences of elevation in different portions of the 
wall. My last observation of the small crater under morn- 
ing illumination was on August 27th. The only opportunity 
I have had of observing it under evening illumination was 
