Flatness And Want Of Contrast. This may be caused by overexposure; by using too large a quantity of developer, thereby washing and add ice for the day; the whole to be covered with a top hinged just back of the baths so as to open both ways - one part to cover the baths, the other to cover the ice-dish. Then the door in front is made so that you may utilize the space under the front of the baths for your collodion and developer; consequently, you have your bath, collodion, and developer all of the same temperature in summer. - Frank Thomas.

At night, when all work is ended for the day, I take my heater to the stove and carefully put a couple of shovelfuls of hot ashes out of the stove into the heater, put on the cover, wipe off any superfluous dust, carry it into the dark-room, and stand the whole thing in the middle of the room on three clean bricks, and in the morning I repeat the operation (leaving the old ashes in the heater, and only taking them out to make room for fresh, but always leaving some in), and my dark-room, after the usual cleaning, is ready for business, and will keep evenly warm until night, as the ashes hold their heat a long time, and are almost as hot at night as when they were put in in the morning. It is a very cheap contrivance and answers admirably, entailing no expense, and being free from disagreeable smells, like coal-oil stoves emit. It will last a lifetime. I made mine myself out of an old five-gallon oil-drum, and any handy man can make his own. - L. A. Weller.

182. When a negative is under-exposed, it will look much like an ambrotype; it is black and white, and generally too intense for a good picture. An over-exposed negative is just the reverse; you can hardly see the image when looking at it by reflected light. Prints from it are flat and gray, face and drapery being nearly of one color. - G. H. Fennemore..

I suggest that when a bath ceases to work well, it is not worth while to waste much time in coaxing it. Success is doubtful, and, if a single trial or two does not succeed, it is better to turn the bath into a bottle, and make a new bath. It is no waste of material, and considerable saving of time and patience. - M. Carey Lea.

183. The introduction of iron for development has almost entirely changed the method of working, and now the rule is to employ a much weaker printing-bath and use subdued light instead of sunlight. The time, however, necessary to produce a print is very nearly the same, notwithstanding the very thin character of the negative as compared with the old ones. I do not, however, wish it to be understood that I consider half a day needful for the off most of the free nitrate of silver, or by using too new a collodion; by plates remaining long in the nitrate bath; by too much time intervening between the removal from the bath and the development, and by the use of too much bromide in the collodion.

184. an apparent formation of network after the film is dry. This may caused by using alcohol that is not absolute, and containing too much water; or, if yon use potassium salts for iodizing or bromizing, you may use too much water in dissolving them. It times caused also by impure ether. Crapy lines are formed by the collodion being too thick; in which case thin it down with iodizing solution. Sometimes they result from the collodion being too gelatinous; in that case add some old limpid collodion do it.

185. Then are two other negative trials which are apt to occur, and which are important to be overlooked. One of these is known production of a print from an average negative of the - present day. The experience of ninny will, however, bear me out in saying that from negatives yielding, in summer, prints full of gradation, the results at this time of year are totally different, and that hardness is the rule; whilst from many negative - that printed respectably in bright weather, presentable results cannot now be obtained at all. On the other hand, many negatives that in very bright weather, even in the most shady street possible, gave flat, poor prints, are now found to yield perfect results. - Valentine Blanchard.

184. A great number of experiments have recently been made in order discover the best method to adopt in the chemical laboratory to detect the presence of water and alcohol in commercial ether. After many trials it appears that the old method, which consists in washing the ether, is, after all, the best. A given quantity of the sample is put into a finely graduated tube; the volume is noted; the same volume of cold distilled water is added; the tube is corked to prevent a loss of ether by evaporation, then the whole is shaken, frequently reversing the tube. When the ether contains alcohol, this last is dissolved in the water; the column of ether which rises to the top is measured with care, and the difference between it and the original volume represents that of the alcohol and water contained in the sample. As ether is slightly soluble in pure water, the results are a little too high. In reality, one hundred parts of water dissolve ten parts of ether, whilst the same quantity of water dissolves an indefinite quantity of alcohol. To be exact, allowance must be made for the quantity of ether which may have been dissolved in making this little experiment - Dr.Phipson.

Should the " lighting " be correct, and the bath yield harsh or black and white plates, be from two causes: 1. Insufficient time of exposure.2. Insufficient iodide in the bath. Should the latter be the cause, coat the largest plate the bath can take on both sides with collodion,and leave it in the solution over night,or at such times when the bath is not in use. - Elbert Anderson.

Where I know that the negative has received too brief an exposure, I expose to the gaslight, regulating my development carefully according to the result; and here (in the density. Negatives afflicted with this are a trouble to the printer, and the prints made from them are usually of an indifferent character. This fault may be in a measure cured by the employment of a reducing process, which is always one which requires the nicest care and a knowledge beforehand of the quality you desire to secure.