GENERAL MEETING. 21 
2 
Easter Sunday = March (22 + 20+ 4=) 46 
== April (46 — 31 =) 15 
232p MEETING. Marca 24, 1883. 
Vice-President WELLING in the Chair. 
Forty-three members and visitors present. 
The first communication was by Mr. J. R. Eastman on 
THE FLORIDA EXPEDITION FOR OBSERVATION OF THE TRANSIT 
OF VENUS. 
[ Abstract. ] 
The observing station of the Florida expedition was upon Way 
Key, the largest of the group of islands known as Cedar Keys. 
The principal instruments employed were a portable transit, a 
five-inch equatorial telescope, and a photoheliograph. The first 
two require no description. The photoheliograph consisted of an 
objective of five inches aperture and about forty feet focus, a helio- 
stat for throwing the sun’s rays on the objective, and a plate holder 
at the focus of the objective. The accessory apparatus consisted 
of a measuring rod, permanently mounted, for accurately measuring 
the distance from the objective to the photograph plate; a movable 
slide with a slit of adjustable width, for exposing the plates; and a - 
circuit connecting with a chronograph, so arranged that when the 
exposing slide was moved to expose the plate, and when the center 
of the slit was opposite the center of the plate-holder, the circuit 
was broken and the record made on the chronograph. A black 
disk was painted on one side of the slide, and so placed that when 
the slide was at rest at one end of its course and the image of the 
sun was adjusted concentric with this disk, it would fall on the 
center of the plate-holder when the slide was moved. The adjust- 
ments having been completed the exposing of the plates was a sim- 
ple matter. The image of the sun was thrown by the heliostat 
upon the black disk and centered, the sensitive plate was fixed in 
