85 
have shown that when the same care has been taken to find 
the actinic focus negatives of a much larger size may be made, 
and in a very short time. The image is increased from eleven- 
sixteenths to one and a quarter inch, and the time of exposure 
at full moon was two seconds. The fittings of the lens are so 
arranged that three different sized negatives may be taken. 
There are several other matters which it might have been 
desirable to refer to had time permitted, but they must stand 
over to a future occasion. 
Mr. Baxendell said that some years ago Dr. Joule had 
obtained several beautiful negatives of the sun. The time of 
exposure was about too- of a second, and the apparatus for 
admitting and cutting off the light was not attached to the 
telescope, as in the Kew heliograph, but was mounted on a 
separate stand. 
PHYSICAL AND MATHEMATICAL SECTION. 
January 4th, 1866. 
E. W. Binney, F.R.S., F.G.S., President of the Section, 
in the Chair. 
Mr. G. Y. Vernon, F.R.A.S., M.B.M.S., was elected 
Honorary Secretary of the Section. 
Mr. Vernon communicated the following “ Remarks on 
the Barometric Disturbances during the Months of October, 
November, and December, 1865.” 
At the last meeting of the Physical Section attention was 
called to the great barometric disturbances in October and 
November of this year ; and in order that their character may 
be seen at a glance I have drawn out my observations made 
twice daily in the subjoined curves. 
