180 THE PHOTOGRAPHIC WORK OF GEOLOGICAL SURVEYS. 
rough work, such as much of that which would have to be done 
in these colonies, and they are very expensive. 
We now propose to give attention to instruments of a simpler 
nature. 
One of the best consists of a rectangular box having an open- 
ing at one end for the purpose of inserting the plate holder or 
dark slide, and a lens in front, with all necessary adjustments 
for levelling and for ensuring the important condition of the 
maintenance of the relative positions of the plate and the objec- 
tive; it is, in fact, a “ fixed focus” camera, the focus being ad- 
justed for parallel rays. 
It should be constructed of metal, and should be perfectly 
accurate. This camera rests on a tripod with levelling screws, 
the tripod head screwing on to an ordinary theodolite tripod 
stand. 
Such a camera is used simply for photographing the views, 
all measurements of angles being made with a theodolite—a 
separate instrument. 
In Canada a simple camera is used; it is a rectangular 
metallic box carrying two sets of cross levels and the photo- 
graphic objective, and it is placed within a mahogany box with 
openings for reading the levels, and having proper fittings at 
the bottom for mounting it on a plate provided with three level- 
ling screws. The lens is a Zeiss anastigmat No. 3, Series V., 
141 m.m. focal length, and an orange screen is used in the 
front. The plate holder or dark slide is inserted loosely, and 
then a screw arrangement, which is provided for the purpose, 
sends it home against the back of the metallic box, so that it 
always occupies the same position during the exposure of the 
plate. The photographic plates used are isochromatic 64 in. x 
42 in., and the angle of view is 60 deg. 
After as many views as may be required are taken from:any 
given station, the camera is taken from the stand, and replaced 
by a theodolite, which fits on the same plate. 
The exposed plates are not developed on the spot, but are 
put up in batches of two dozen, packed in double tin boxes, and 
forwarded to Ottawa for development. 
The committee is of opinion that this report, taken with the 
previous one, deals with all the important points of the ques- 
tion, and suggests that, as this work is of a national character, 
and as it is important that the same system should be observed 
throughout Australasia, the council of the association should 
approach the Federal Government after its constitution with a 
view of impressing upon it the importance of proceeding with- 
out delay, with the aid of photography, in the commencement 
of the topographical and geological survey of the whole of the 
territory which is under its control. 
J. H. HARVEY, A.R.V.LA., 
Secretary to the Committee. 
