The book of lantern ; being a practical guide to the working of the optical (1888)

Record Details:

Title:
The book of lantern ; being a practical guide to the working of the optical
Date:
1888
Publisher:
London : Wyman & Sons
Volume:
The book of lantern ; being a practical guide to the working of the optical (or magic) lantern ; with full and precise directions for making and colouring lantern pictures
Leaf #:
000131
Language:
English
Collection:
Books
Format:
Books
Contributor:
University of California Libraries
Sponsor:
MSN
Coordinator:
Media History Digital Library
Date Added:
July 19, 2022
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118 THE BOOK OF THE LANTERN. other words, " the intensity of illumination on a given sur- face is inversely as the square of its distance from the source of light" FIG. 39. Fig. 39 will perhaps make the matter still more plain. At 1 foot from the candle the square marked i receives a certain amount of light; at u, that light is spread over a surface four times the area of the first ; and at in over a surface nine times as large as I. This law, which is really of a very simple character, the operator should have con- stantly in his mind, as he exposes his plates, to artificial light under a negative. The method of development which I recommend is by means of ferrous oxalate, and it will be found that the transparencies produced by- it require no toning whatever. I make my own potassic oxalate, and find it, moreover, reliable; the operation is simplicity itself. In a large basin dissolve half a pound of carbonate of potash (salts of tartar) in a pint and a half of warm water. Now add gradually oxalic acid, a few cr3 T stals at a time, for the effervescence is very violent, and difficult to control if much be put in at once. When six ounces of the crystals