Page:Madras journal of literature and science vol 2 new series 1857.djvu/265

Rh changed the right one becoming the left and vice versâ. Whilst for glass positives it is necessary to use separate glasses, the frame having a smaller central support as below. As the centre of the lenses in taking Stereoscopic pictures is a little above the centre of the Camera, the position of the glass plate must be made to correspond.

I do not observe that the glasses being parallel instead of converging towards the object makes any perceptible difference in the pictures, but when a table is used to support the Camera, such convergence might be easily given by having a pivot under the front of the Camera and limiting its lateral motion by screws placed as in the accompanying figure F.

I have found it impossible to get made here the rather complicated exposing frame usually described in books on taking Stereoscope pictures, when a system of parallel bars is used on a table to shift the Camera and at the same time to move the collodionized plate. With a Camera constructed as above the parallel frame might be used with advantage for groups of figures and distant objects, moving

the object glass in a direction contrary to that given to the Camera, when the pictures would be in their correct places on the glass. I send enclosed a picture or two which will show that