96 
PHOTO GRAPHI CAL SECTION. 
January 11th, 1866. 
Dr. J. P. Joule, F.R.S., & c., Vice-President of the Section, 
in the Chair. 
A note from Mr. Joseph Sideboth^m was read, regretting 
his inability to attend the meeting, and giving particulars 
respecting some photographs which he had recently taken 
with Dallmeyer’s new wide-angle lenses of five and seven 
inches focus. These prints were exhibited, and also one 
taken with an ordinary lens from the same spot, a compari- 
son of the two showing the great advantage of the new over 
the old form of lens. The time of exposure was stated to be 
from two minutes to thirty seconds for collodio-albumen 
plates at this season of the year. 
Professor Roscoe explained the method of meteorological 
registration of the chemical action of light, as described in 
his paper in the Philosophical Transactions of the Royal 
Society, which has been chosen as the Bakerian lecture for 
1865. Dr. Roscoe exhibited the apparatus needed, and 
showed the method of manipulation adopted in order to 
obtain curves of daily chemical intensity. He also detailed 
the results which have been obtained by the employment of 
his method at the British Association’s observatory at Kew, 
during nine months of the year 1865, under the superintend- 
ence of the Director, Mr. Balfour Stewart, F.R.S. 
Dr. Joule observed that he considered Dr. Roscoe’s inves- 
tigations on this subject to be equal in importance to the 
