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ine from two to three seconds。
Bromide of Lime； or Dry Sensitive。This is a compound but recently introduced； and is becoming somewhat of it favorite； owing principally to the slight trouble it gives in its preparation； and the tone it imparts to the picture。 To prepare it； fill your jar about half or quarter full of dry slacked lime； then drop into it bromine； till it becomes a bright orange red。 The plate is generally coated over this compound； after the iodine coating to yellow； to a violet； or plum color； but it will work well under any circumstances； the color being of little consequence； if coated from thirty to ninety seconds； according to its strength。
Mead's Accelerator。I merely mention this as being in the market； not knowing any thing in regard to its merits。 The directions given for its use are as follows： Mix one…third of a bottle with a wine glass full of water； coat the plate over dry iodine to a dark gold color； then over the accelerator to a violet； then back over dry iodine； or chloride of iodine； from three to five seconds。
Chloride of Bromine。M。 Bissou； a French experimentalist； has found that bromine associated with chlorine； prepared in a similar manner to chloride of iodine； already described； a solution of bromine being substituted for the iodine； is a very sensitive solution； by means of it daguerreotype proofs are obtained in half a second； and； thus very fugitive subjects are represented； making it the very best compound for taking children。 So quick is its operation； that even persons or animals may be taken in the act of walking。
Hungarian Liquid。This； I believe； has never been used here； or imported into this country； and the composition of it is not generally known； even in Europe； where it has taken precedence of all others。 It acts quickly and with considerable certainty。 It is used by diluting it with from ten to fifteen times its bulk of water； putting a sufficient quantity into the jar to cover the bottom。 The plate being previously iodized to a light yellow； is submitted to this mixture till it assumes a light rose tint。
Bromine and Fluoric Acid； in combination； are used by some Daguerrean artists as a sensitive； but any of the above compounds are better； besides this； the fluoric acid is a dangerous poison； and the quick made from it will not repay the risk to the health in using it。
As I have before said； great caution should be observed in examining the color of the plate； even by the feeble light allowed； which； when attained； must be immediately placed in the holder belonging to the camera and covered with the dark slide。 You then pass to the
THIRD OPERATION。Submitting the Plate to the action of Light in the Camera。Experience alone must guide the operator as to the time the plate should be exposed to the influence of the light； this being dependent on a variety of circumstances； as clearness of the atmosphere and here； a reference to the hygrometer will be of advantage time of day； object to be taken； and the degree of sensitiveness imparted to the plate by the quickstuff。 As I have before said； the artist should be careful to see that the interior of the camera is clean and free from dust； as the small particles flying about； or set in motion by the sliding of the holder into the box； attach themselves to the plate； and cause the little black spots； by which an otherwise good picture is frequently spoiled。 Care should also be taken in withdrawing the dark slide； in front of the plate； from the holder； as the same effect may be produced by a too hasty movement。 The lens is the last thing to be uncovered； by withdrawing the cap c。 fig。 5。； which should not be done until you have placed the sitter in the most desirable position。 When； according to the judgment and experience of the operator； the plate has remained long enough to receive a good inpression； the cap is replaced over the lens； and the dark slide over the plate； which is then removed from the camera。
Daguerreotypists generally mark time by their watches； arriving at the nearest possible period for producing a good picture by making several trials。 As a ready method of marking short intervals of time is； however； a very important consideration； and as any instrument which will enable an artist to arrive at the exact period； must be an improvement； and worthy of universal adoption； I will here describe one invented by Mr。 Constable of England； which he calls a
Sand Clock； or Time Keeper。〃It consists of a glass tube； about twelve inches long； by one in diameter； half filled with fine sand； similar to that used for the ordinary minute glasses； and； like them； it has a diaphram； with a small hole in the centre through which the sand runs。 The tube is attached to a board which revolves on a centre pin； on the side is a graduated scale； divided into half seconds； the tube is also provided with a moveable index。 This instrument is attached； in a conspicuous place； to the wall。 The glass tube being revolved on its centre； the index is set to the number of half seconds required； and the sand running down； the required time is marked without the possibility of error。 In practice it will be found to be a far more convenient instrument for the purpose than either a clock or a seconds watch； and is applicable both for the camera and mercury box。〃
If the artist finds it desirable or necessary to take the object to be copied in its right position； that is reverse the image on the spectrum； he can do so by attaching a mirror （which may be had of Mr。 Anthony； or Mr。 Roach） to the camera tube； at an angle of forty…five degrees。
If； after taking the plate from the camera； it be examined； no picture will yet be visible； but this is brought about by the
FOURTH PROCESS。Bringing out the Picture； or rendering it Visible。 We now come to the use of the mercury bath； Fig。 11。 To the bath a thermometer is attached； to indicate the proper degree of beat required； which should never be raised above 170 deg。 Fahrenheit。 The plate maybe put into one of the frames （see Fig。 11；） over the mercury； face downwards； and examined from time to time； by simply raising it with the fingers； or a pair of plyers。 This operation； as well as the others； should take place in the dark closet。 ＇hipho_26。gif＇ Sometimes； to prevent the necessity of raising the plate； an additional cover or top is made use of。 It consists of a box fitted closely to the inner rim of the bath； and having an inclined top （a； Fig。 27。） The top is cut through and fitted with frames for each size of plate； like those already described； and in the back is a piece of glass （b；） through which to view the progress of mercurialization； and an additional piece （c；） on one side； colored yellow； to admit the light。 The outline only of the top is here given； in order to show every portion of it at one view。
The picture； being fully developed； is now taken out and examined； it must not； however； be exposed to too strong a light。 If any glaring defects be perceived； it is better not to proceed with it； but place it on one side to be re…polished； if； on the contrary； it appears perfect； you may advance to the
FIFTH OPERATION。Fixing the Image so that the light can no longer act upon it。The following articles are required for this purpose：
Two or three porcelain or glass dishes； in form； something like fig。 24。
A plate support； fig。 25。 Few； I believe； now make use of this； although it is a very convenient article。
Hyposulphite of Soda；
A pair of Plyers。
In Europe； they also use a drying apparatus； Fig。 27； but this； like the plate support； ＇hipho_27。gif＇ is a matter of little consequence； and may be dispensed with。 I will； however； describe it； for the benefit of those who may wish to use it。
A vessel made of copper or brass； tinned inside； and large enough to take in the largest plate； but not more than half an inch wide； is the most convenient。 It must be kept perfectly clean。 Hot distilled water is poured into it； and the temperature kept up by a spirit lamp。
Hyposulphite of Soda。Having made a solution of hyposulphite of soda； and well filtered itthe strength is immaterial； about half an ounce of the salt to a pint of distilled water is sufficientpour it into one of the porcelain dishes； put into another plain； and into a third distilled water。 Immerse the plate with its face downwards into the hyposulphite； and the whole of the sensitive is removed； and the light has no farther action upon it； it is then to be removed from the hyposulphite and plunged into the plain water； or placed upon the support； fig。 25； and the water poured over it。 It is then washed in a similar manner with the distilled water and well examined； to see that not the slightest particle of dust rests on the suface。 The next step is to dry it。
This may be readily accomplished by holding the plate with your plyers； and pouring distilled water over itif it is hot； so much the better。 Apply the spirit lamp to the back； at the corner held by the plyers； at the same time facilitating the operation with the breath； pass the lamp gradually downwards； finishing at the extreme corner。 The last drop may now be removed by a little bibulous paper。 A single drop； even； of distilled water