"We are always glad to note every step which our mechanics make towards improvement on the apparatus used by our practical photographic operators, and make the present announcement of one which has only to be known to be readily understood, and to be seen to be appreciated. A patent has recently been granted for making solid glass corners, which are to be attached to plate-holders, and form the most perfect article that has ever been introduced. Heretofore the operator has had the corners of his plate-holders made with separate pieces of glass, cut so as to fit the corners of his frames; these are only glued or grooved in, and are constantly coming apart, falling out, and annoying in many ways; for our part, we never have considered them as fit for use in any manner. We look upon the present improvement as destined to entirely supersede all the methods heretofore introduced. In this case the collodionized or albumenized plate can come in contact with no other substance than a single piece of glass, and consequently there is far less liability of accident from either the staining of the plate or breaking of the holder. The rapid favor this improvement has gained already shows its great advantage over all other methods heretofore employed." ] "Decomposition by exposure to light or by long keeping, even in the dark. The author conceives that it is possible for organic matter alone to produce, after a time, a partial decomposition of solution of nitrate of silver, sufficient to prevent it from being employed chemically neutral, but probably not much interfering with its properties in other respects. "Use of rain water or of water containing carbonate of silver being perfectly neutral and from nitric acid. This difficulty is not a theoretical one only, but has actually been experienced. Rain water usually contains ammonia, and has a faint alkaline reaction. Pump water often abounds with carbonate of lime, much of which, but not the whole, is deposited on boiling. To remove the alkaline condition, add acetic acid, one drop to half a pint of the solution. "Partial decomposition of the bath, by contact with metallic iron, with hyposulphite of soda, or with any developing agent, even in small quantity. Also by the use of accelerators, which injure the bath by degrees, and eventually prevent its employment in an accurately neutral state. "Vapor of ammonia, or hydrosulphate of ammonia, escaping into the developing room."