His method is to fix at the bottom of a tube, blackened within, a piece of card, on which chloride of silver, mixed with gum or dextrine, is spread.

The tube thus disposed is turned from the side of the object of which we wish to take the image, and the time that the chloride of silver takes to become of a greyish slate color will be the time required for the light of the camera to produce a good effect on the iodated silver.
INSTANTANEOUS PROCESS FOR PROCURING DAGUERREOTYPES.
The following method of producing Daguerreotypes has by some been named as above.

Most experienced operators have been long acquainted with the effect of the vapor of ammonia upon the chemically coated plate.

I will here insert Mr.W.H.Hewett's plan of proceeding.

This gentleman, in referring to it (published in 1845), says: "This improvement consists in using the vapor of ammonia, as an object to accelerate the action of light upon the plate.