STILL.--Daguerreotypists should always use distilled water for solutions, and washing the plate, as common water holds various substances in solution which detract very materially from the excellence of a photograph, and often gives much trouble, quite unaccountable to many. For the purpose of distilling water the apparatus represented at Fig. 16 is both convenient and economical.
It may be either wholly of good stout tin, or of sheet iron tinned on the inside, and may be used over a common fire, or on a stove. A is the body, which may be made to hold from one to four gallons of water, which is introduced at the opening b, which is then stopped by a cork. The tube d connects the neck a of the still with the worm tub, or refrigerator B, at e, which is kept filled with cold water by means of the funnel c, and drawn off as fast as it becomes warm by the cock f. The distilled water is condensed in the worm--and passes off at the cock b, under which a bottle, or other vessel, should be placed to receive it. The different joints are rendered tight by lute, or in its absence, some stiff paste spread upon a piece of linen and wrapped around them will answer very well; an addition of sealing wax over all will make them doubly secure.
HYGROMETER.--This is an instrument never to be found, I believe, in the rooms of our operators, although it would be of much use to them, for ascertaining the quantity of moisture floating about the room; and as it is necessary to have the atmosphere as dry as possible to prevent an undue absorption of this watery vapor by the iodine &c., and to procure good pictures,--its detection becomes a matter of importance. Mason's hygrometer, manufactured by Mr. Roach and sold by Mr. Anthony, 205 Broadway, New York is the best in use.
It consists of two thermometre tubes placed, side by side, on a metalic scale, which is graduated equally to both tubes. The bulb of one of these tubes communicates, by means of a net-work of cotton, with a glass reservoir of water attached to the back of the scale. Fig. 17 and 18 represent a front and back view of this instrument.
Fig. 17 is the front view, showing the tubes with their respective scales; the bulb b being covered with the network of cotton communicating with the reservoir c fig. 18, at d.
The evaporation of the water from this bulb decreases the temperature of the mercury in the tube b in proportion to the dryness of the atmosphere, and the number of degrees the tube b indicates below that of the other, shows the real state of the atmosphere in the room; for instance, if b stands at forty and a at sixty-one the room is in a state of extreme dryness, the difference of twenty-one degrees between the thermometers--let a stand at any one point--gives this result. If they do not differ, or there is only four or five degrees variation, the atmosphere of the room is very moist and means should be taken to expel the superfluous quantity.