bichloride of mercury. The thing that strikes us as remarkable in
connection with them is that in them the image has scarcely suffered any
reduction of intensity at all. In most cases there has been a disagreeable
change of color, but it is almost entirely confined to the whites and
lighter tints, which are turned to a more or less dirty yellow. Even in the
case of the prints toned by bath No. 10, where the image is quite red, it
has suffered no appreciable reduction of intensity.

This would indicate that an unusually large proportion of the toned image
consists of gold, and this idea is confirmed by the fact that to tone a
sheet of gelatino-chloro-citrate paper requires several times as much gold
as to tone a sheet of albumenized paper. Indeed, we believe that, with the
emulsion paper, it is possible to replace the whole of the silver of the
image with gold, thereby producing a permanent print. We have already said
that the print may be left for any reasonable length of time in the toning
bath without the destruction of its appearance, and we cannot but suppose
that a very long immersion results in a complete substitution of gold for
silver.

* * * * *




THE "SENSIM" PREPARING BOX.


Fig. 1 shows a perspective view of the machine, Fig. 2 a sectional
elevation, and Fig. 3 a plan. In the ordinary screw gill box, the screws
which traverse the gills are uniform in their pitch, so that a draught is