the risk of over-exposure.

To test the safety of your camera--Half draw the shutter, and expose
part of the plate in the camera, in the sunshine, without uncapping
the lens, and develop.

To test the safety of your red light--Expose a plate, divide it into
two, develop half in the dark, and half for the same time, with the
same solution by the light you are testing, and compare the results.
This test is worth making, as photographers are apt to give
themselves much discomfort from exaggerated caution.

2. Itinerary.

Where there are efficient maps the only need is to mark in the
position of any antiquities, by cross-bearings to clear points, with
the compass, drawn in with a sharp pencil. Where the maps are too
small, or deficient, a continuous register of time should be made,
noting the minute of starting and of stopping; this over known
distances will serve to give the value over the unknown. Note whether
mounted or walking, and the compass bearing of the track; also the
bearings of known points around, whenever stopping. Without any known
bearings pacing and compass used carefully may go over the roughest
ground without five per cent. error in the day.

It is better when on unknown ground to plot a map as you go, so that
no misunderstanding of notes can arise after. If a squared block
cannot be used, at least draw the bearings and distances roughly,
writing in the amounts. This should be plotted up accurately in the
evening. A photograph may be unintelligible later in its detail. It