In working with gelatine plates various unavoidable accidents and faults will crop up, some of which can, however, be remedied. Such cases we will now go into.

Gives chalky whites and sooty blacks, ergo no tonality, erqo worthless. No remedy, destroy at once.

Underexposure. Overexposure

Gives thin negatives. What a thin negative is, is a matter of opinion, and must be settled by a comparison of the print with the impression of nature which it is wished to obtain. For many effects thin negatives are invaluable, and the student must not take the ordinary photographer's opinion as to his negatives; but only that of an artist, for, as has been shown, low-toned prints are unrecognized by the ordinary craftsman, his aim and object is never to produce such things, these he designates by all sorts of names, whereas they may be, by their tonality, infinitely truer than his "sparkling" falsehoods. In short, it all depends on what the student wishes to express. Some of the best work done has been produced from negatives made purposely thin, which have at the same time been true in tone, and full of breadth. The density of a negative can be increased by intensifying the negative; but it must not be forgotten that intensification does not, in our opinion, correct the tonality, this is a matter of great importance which has been overlooked. From this it will be seen that a negative that requires intensification is worthless for artistic purposes, and had better be destroyed at once. But as intensification may be required for some particular object, we must caution the student against the ordinary perchloride of mercury and ammonia intensifier. In many cases it acts well enough, in many others it acts unevenly and in patches, and in all cases it is not permanent. The best intensifier we know of is Dr. Eder's, whose formula we give -

Intensifi-Cation. Dr. Eder's Intensifier

Wash the plate thoroughly after fixing, so that no hyposulphite remains, and immerse in the intensifies It works up the scale from the lower tones, which is an advantage over any other. To remove all the hyposulphite of soda it is well to treat the plate before using the intensifier, as Captain Abney directs. A drachm of a 20-vol. solution of peroxide of hydrogen should be mixed with 5 oz. of water, and the plate soaked in it for half an hour, and then washed.