The Total Solar Eclipse of 1900. 73 
Kinematograph. 
The conditions required to be fulfilled by this instrument were somewhat 
difficult. 
It was required that some twelve photographic plates should be exposed to the 
image of the spectrum during about the same number of seconds, and that there 
should be absolutely no interval between the successive exposures, so that if any 
flash-lines made their appearance, even for a moment, during those 12 secs., their 
images should certainly be impressed on some one of the plates. 
In any ordinary form of kinematograph there must be a sensible interval 
between the exposure and each successive plate; therefore it was necessary to 
devise a special apparatus to fulfil the above conditions. | 
A strong steel shaft is mounted in the centre of a camera-box, passing verti- 
cally through stuffing-boxes in top and bottom, so as to be capable of smooth and 
easy motion in a vertical direction. An arm on this shaft, working against a 
knife-edge, with spring to keep the arm in contact, prevents this plunger from 
turning on its axis, or from any motion except one purely vertical, and this 
plunger carries a pair of silvered mirrors, long and narrow in form, and mounted 
over one another, with their reflecting surfaces at right angles to each other. (See 
figs. 4 and 5.) 
These mirrors are placed in the path of the rays, between the object-glass and 
prism, and the image as formed on the photographic plate. 
When the plunger is at its highest position, the rays fall on the lower mirror, 
and are directed at right angles to one side of the camera, while in its lowest 
position the rays fall upon the upper mirror, and are directed to the other side of 
the camera, and on to the other photographic plate. Moving the plunger there- 
fore up and down has the effect of throwing an image of the spectrum alternately 
on each plate, and in an intermediate position partly on both plates, and there 
is absolutely no interval of time in which the spectrum is not thrown on one or 
other. 
The hexagon drums which carry the six plates are attached to each side of the 
camera in slides, and by a simple piece of mechanism each drum is moved forward 
a sixth of a turn during the time that the plate on the opposite drum is exposed, 
so that by the time the other plate has been exposed, and the mirrors shifted, a 
fresh plate is presented to the image on the first side, and so on. The move- 
ment of the mirrors in a vertical direction being absolutely in the plane of the 
mirrors themselves, produces no shifting of the image on the plate, and therefore 
no indistinctness. 
TRANS. ROY. DUB. SOC., N.S., VOL. VIII., PART V. O 
