Circle of Least Confusion Claude Lorraine Glass
projector of the same firm. The cross-like shutter covers the lens at the instant when the film is moved, so as to bring another view into the field, the whole play of movement being controlled by the winch handle. (For general principles of this and other similar lanterns see Zoetrope.)
The Kammatograph. Those ordinary types of cinematograph, which involve the use of a long band of film, are rather incon-venient in the hands of the amateur, as the band of film - often several hundred feet long - is by no means easy to deal with in an ordinary dark room. To meet this difficulty, Mr. L. Kamm has designed an apparatus by which between 500 and 600 small views can be taken in rapid succession on a circular glass plate
12 ins. in diameter. This negative plate is developed quite in the ordinary way, and a contact transparency made from it on a similar disc is used in a suitable projecting lantern. The kammatograph camera is by no means the enormous construc-tion which might be supposed from the fact that it takes a glass plate 12 ins. in diameter, as it is but little more than large enough to accommodate the plate, the dimensions being 14 ins. x
13 ins. x4^ ins., while the weight is only 8 lbs.
Those who wish to fully study details of the various forms of cinematograph should refer to Mr. Henry V. Hopwood's " Living Pictures," a volume of 276 pp., published at the offices of The Optician, 125, Fleet Street, London. In this work there is an exhaustive bibliography of papers relating to the cinematograph, and a list of patents bearing on the matter.
Circle of Least Confusion. An optical term to denote the nearest approach to an absolute focus of a pencil of light.
Citric Acid (Ger., Citronensaure; Fr., Acide citrique; Ital., Acido Citrico). H3C6H5Or Occurs naturally in the juice of many fruits, and is obtained chiefly from the lime and lemon juice by heating and adding chalk, collecting the precipitate and decomposing with sulphuric acid, and evaporating the solution till crystals are obtained. Solubility: 133 per cent, in cold, 200 per cent, in hot water, soluble in alcohol and ether. It is used to make citrates, as an ingredient of clearing solutions, and as a preservative for sensitised paper.
Claude Lorraine Glass. A plate of black glass, one side of which is ground to a convex figure. Used by painters as showing