PRESIDENTIAL ADDRESS. 27 
turned together through any determined angle. Measure- 
ments of the light intensities were made with a 
Lummer-Brodhura photometer, arranged for equality of 
contrast. Tables and curves are given showing the 
results obtained at varying incidences with different types 
of plain glass and silvered surfaces. The initial superiority 
of silver before glass is about 6 per cent., but when the 
factor is considered, the silver behind glass is much more 
permanent in reflecting power. Thus a_ silver-fronted 
mirror after three months’ exposure had fallen to 
68 per cent., whereas an ordinary commercial back- 
silvered mirror at least three years old, was still capable 
of reflecting 86°7 per cent. of the incident light. 
Lectures on Meteorology.—The Council of the Royal 
Meteorological Society, London, being desirous of advanc- 
ing the general knowledge of Meteorology and of promoting 
an intelligent public interest in the science, has appointed 
a lecturer, who is prepared to deliver lectures to scientific 
societies, schools, and institutions, on payment of a 
moderate fee and the cost of travelling expenses. The 
subjects are:—How to observe the weather, weather 
forecasting, climate, rainfall, thunderstorms, meteorology 
in relation to agriculture, health, etc. The Society is 
also prepared to lend and fit up a complete climatological 
station for exhibition, showing the necessary instruments 
in position and ready for use, and to lend, for a nominal 
sum, sets of lantern slides illustrating meteorological 
phenomena. This is work that could with advantage be 
introduced and carried on in our State. 
Bruce Telescope of Yerkes Observatory. —Details are 
given of the construction and performance of an important 
addition to the instrumental equipment of the Yerkes 
Obser vatory—a photographic doublet of 10 inches aperture 
equatorially mounted, with subsidiary companion teles- 
