The Daguerreotype and its Applicatmis. 139 



tus for small plates, may be made by covering a large capsule con- 

 taining a small quantity of mercury, with a piece of paste-board, 

 with an aperture in it of the size and form of the plate. The 

 mercury should be raised to about 140°, and the paste-board laid 

 in its place. The frame containing the plate which has received 

 the image, should then be placed horizontally ovex the aperture 

 and the slide withdrawn. I have employed an apparatus of this 

 description very successfully ; and have found it advantageous to 

 separate the plate farther from the mercury than the depth of the 

 capsule ; for this purpose, a paste-board box, open at both ends, 

 two or three inches in length, and a little larger than the aperture, 

 may be placed over it to support the frame. The proof will ap- 

 pear in five or ten minutes."* 



Most if not all of these modifications of the Daguerreotype ap- 

 paratus were first effected by Professors Draper and Morse of the 

 University of New York. 



Plates for Daguerreotype purposes are either of American man- 

 ufacture, or they are imported from France. American plates are 

 exceedingly imperfect. The silver abounds with perforations, 

 which appear as black dots in the pictures ; it also assumes a yel- 

 low instead of a white coat in burning. 



A method has recently been published by Dr. Garlick, of pla- 

 ting brass or copper, which probably will remedy many of the 

 difficulties now encountered in procuring plates of a good quality. 

 In using these plates, the usual routine of cleaning, burning, &c. 

 is unnecessary. 



A piece of brass, or of planished copper — brass is preferred — is 

 perfectly polished and its surface made perfectly clean. A solu- 

 tion of nitrate of silver, so weak that the silver is precipitated 

 slowly, and of a brownish color, on the brass, is laid uniformly 

 over it, "at least three times," with a camel's hair pencil. After 

 each application of the nitrate, the plate should be rubbed gently 

 in one direction, with moistened bitartrate of potassa, applied with 

 buff. This coat of silver receives a fine polish from peroxide of 

 iron and buff. Proofs are said to have been taken on it, compar- 

 able with those obtained on .French plates. 



* Mr. H. L. Smith of Cleveland, Ohio, is in the habit of employing the vapor of 

 mercury spontaneously given off from amalgamated copper for bringing out the 

 picture. If the amalgam is evenly spread on the copper surface, the iodized plate 

 may be placed within half an inch of it ; but if the mercury is in a fluid state, the 

 iodized plate should be separated double that distance. 



