8. _Intensifying solution._--Pyrogallic acid, 6 grs.; glacial acetic acid, 1/4 oz.; distilled water, 6 ozs.; mix. A few drops of a 30-gr. solution of nitrate of silver, the quantity to be regulated according to the intensity required, to be added, at the moment of using, to as much of the pyrogallic solution as may be necessary. _Intensifying solution_ (another form).--1. Pyrogallic acid, 8 grs.; citric acid, 20 grs.; distilled water, 2 ozs. 2. Nitrate of silver, 8 grs.; distilled water, 2 ozs. Mix small quantities of the solutions 1 and 2, in equal portions, the moment before using. The pyrogallic solution, made with good acetic acid, may be kept for a month or more in a cool place. Nevertheless, if the conditions of light and situation are unfavorable, I should prefer this solution just made. The iron solutions act best when freshly prepared. It is supposed by some that a prolonged action of the iron developer produces fogginess. This may be the case when impure or improperly prepared collodion is used, but certainly not when the preparation is pure and of the proper quality. When the image is sufficiently intense, wash freely with common filtered water; then pour on a saturated solution of hyposulphate of soda, which should immediately remove the iodide of silver: wash again well with water; allow as much as the plate will hold to soak in for at least a quarter of an hour, changing the water occasionally, to remove all traces of hyposulphate; lastly, wash the plate with a little distilled water, stand up to dry, and, if required, varnish either with spirit or amber varnish. The following solution is also very commonly used for fixing the negative:--Cyanide of potassium, 1/4 oz.; water, 12 ozs. Attention to the following rules and cautions will assist the operator in the production of perfect pictures:-- 1. Do not disturb the deposit which will occasionally be found at the bottom of the bottle containing the collodion. 2. Remove all particles of dried film from the neck of the bottle before pouring the collodion on the plate. 3. Never use damp cloths, leathers, or buffs, for giving the final polish to the plate. Negatives with an indistinct and muddy surface are frequently produced from this cause. 4. Let the film set properly before immersion in the nitrate of silver bath: its condition can be ascertained by gently touching the lower part of the coated plate with the end of the finger. 5. Never omit to pass a broad camel-hair brush over the plate just before pouring on the collodion.