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In explanation of the four prints being on one plate, Mr. 
Brothers stated that the slide he used for astronomical 
photography is arranged so that four negatives of the sun 
or moon can be taken on the same plate, an advantage 
which he had found of much importance in this kind of 
work. The time occupied in taking the four negatives on 
plate No. 3 was thirty seconds, No. 4 twenty-five seconds; 
and the last set was taken in twenty seconds — an average 
of five seconds for exposing and changing the position of the 
plate. 
Two of the prints, 3 and 4 of the series, were mounted, 
in reversed order, for the stereoscope, and they exhibit very 
good stereoscopic effects although taken from the same 
station, the difference in the position of the moon in an 
interval of about seven minutes being sufficient for the 
purpose. The negatives on No. 3 were taken at 9 h 32 m to 
9 h 32 m 30 s , and those on No. 4 at 9 h 39 m to 9 h 39 m 25 s 
Mr. Brothers also exhibited a photograph on canvass 
printed without the aid of bitumen of Judea or gelatine, or 
of any other substance likely to change by time. The print 
is so completely stained into the canvass as prepared in the 
ordinary way for artists, that it cannot chip or rub off. 
Another advantage is that hyposulphite of soda is not 
required to fix the image. 
