EXCITING THE PREPARED PLATE.

THE plate should he plunged into the exciting bath with a steady hand, and at one motion; the slightest halt will produce a line across the plate, which will impair it, if it does not entirely render it useless.

It should remain in the bath until the surface of the plate presents, on its withdrawal, an even surface of iodide of silver, and the liquid runs off in one continuous sheet, not in lines, the latter always indicating a too short immersion, and shows that the saturation of the film with iodide of silver is not completed.

When the liquid runs off in an uniform sheet, it may he taken as a sure indication, also, that the plate has attained its greatest sensibility; consequently, no advantage will be gained by leaving it in the bath after the saturation is completed.

The time necessary for the plate to remain in contact with the exciting solution will depend very much upon the temperature at the time, and on the quality and thickness of the iodized collodion. In warm weather this saturation is more quickly accomplished than when the temperature is low; from two to three minuites may be required.

By attending to the indications above described, the proper time for removal is easily ascertained.

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