principle of the stereoscope w'as due, proved the fallacy of this. In monocular vision objects on the true optical axis line are distinctly seen, but other objects less so, although they are in the circle of vision, and in this particular the similarity of the lens and the human eye is very evident. Monocular vision can judge the direction, but not the distance of an object.
MotOSCOpe. An apparatus of the Cinematograph class. (See Cinematograph.)
Mountant. The substance used to make the print adhere to its mounts. It is absolutely necessary that the mountant should be free from acidity, in order to prevent the destruction of the delicate image. There are several kinds in common use - viz., starch paste, arrowroot, gum, dextrine, india-rubber solution, liquid glue, and gelatine.
Starch Mountant. Starch in powder I oz. ; mix into a cream with i oz. of water, and add to it, constantly stirring,ozs. of boiling water in which 20 grs. of common alum and 5 drops of carbolic acid have been dissolved. The mixture should be now a clear translucent jelly free from lumps ; if it is not, it should be gently heated in a dish or pan till it clears, constant stirring being an absolute necessity; then it should be squeezed through fine muslin. Ordinary household flour makes a more adhesive paste, but is liable to acidity. Both will keep fit for use about a week, after which they should be rejected.
Arrowroot Mountant, called Permanent Paste. Dissolve by the aid of gentle heat
Arrowroot ... ... ...... ... 150 grs.
Gelatine ... ... ...... ... 150 ..
Distilled water ... ... ... ... 3 ozs.
When cool, add
Methylated spirit............ .drms.
Carbolic acid ... ... ... ... 3 drops.
Gum Solution, or Mucilage. Pale-coloured gum arabic in clean lumps, 4 ozs. ; distilled water, 8 ozs. Wash the gum by placing'it in a half-pint cup or measure ; add half-pint of water ; stir briskly round twice or three times, and pour off the water: this carries off any dust or mechanical impurities. Now add the distilled water, and stir frequently at intervals till dissolved.