Plates, coated and exposed to light in our usual manner of operating, produced on exposure of 1/2 minute, whole impression, deep blue.
1 minute, ashy and flat; no shadows; linen, deep blue.
1 1/2 minute, coarse and spongy; shadows, muddy; drapery, dirty reddish brown.
2 minutes, shallow or watery; shadows, yellowish; drapery, brown.
2 1/4 minutes, soft; face, scarcely white; shadows, neutral; drapery, fine dark brown linen somewhat blue.
2 1/2 minutes, clear and pearly; shadows, clear and positive, of a purple tint; drapery, jet black, with the dark shades slightly frosted with mercury.
2 3/4 to 3 minutes, hard and chalky; shadows, harsh; drapery, roughened, and misty with excess of mercury.
The foregoing results will be found general.
There are numerous opinions among our operators in regard to the quantity of mercury necessary for a bath.

As regards this, I need only say, similar results occur when two pounds or two ounces are used, but the quantity generally employed is about a quarter of a pound.

I am of the opinion that one ounce will answer as well as a larger quantity.

I know of no better proof in favor of a small quantity than that presented in the following incident.

Several years since, an operator (Mr.Senter, of Auburn, N.Y.) of my acquaintance, was requested to go several miles to take a Daguerreotype portrait of a deceased person.
He packed up his apparatus and proceeded over a rough road for some distance to the house where he was to take the portrait, and arranging his apparatus, with all the expedition which the occasion required, after having everything in usual order (as was supposed), he proceeded and took some ten or twelve very superior impressions.