1 .-- This mixture was used by me in 1849, and is given as it appeared in my "System of Photography," published at the above date: Take pure rain or distilled water, one quart, filter through paper into a ground stopper bottle, and add, for warm weather, one and a half ounce chloride of iodine; or for cold, one ounce; then add one ounce bromine, and shake well.

Now with care not to allow the vapor to escape, add drop by drop, thirty drops of aqua ammonia, shaking well at each drop.

Care must be taken not to add more at a time, as it evokes too much heat.

This mixed, in equal proportions with John Roach's quick, forms an excellent chemical combination.

For this purpose, take one and a half ounce of each, to which add ten ounces water, for warm weather, or from six to seven for cold.