Camphor Canada Balsam
an experimental station, no system is so generally convenient as that in which the camera looks down, as these diagrams from books, natural history specimens, anatomical work in progress, and also specimens resting in dishes of liquid, can all be photo-graphed with but little delay and inconvenience. In Figs. 20 and 21 we show two arrangements for the support of the camera vertically. Fig. 20, that of J. E. Prowse (The Amateur Photo-grapher, January 2nd, 1902), and Fig. 21, that of Dr. Donna-dieu; the former easily constructed by an amateur, while the latter is a more expensive device suited for a public institution. When a transparent object is to be photographed it can be laid on a sheet of plate glass used as a stage ; a mirror set under-neath at a suitable angle directing the light upwards. It maybe suggested that in using the vertical camera, it will generally be undesirable to put the apparatus on the table, but rather on the floor ; indeed the photographer may often have to himself mount upon the table. If the camera is definitely set or adjusted for a certain focal plane, special focussing can often be avoided ; but a more complex system of datum marks and adjustments for various scales of reduction is often convenient.
Camphor (Ger., Camphor; Fr., Camphrc; Ital., Canfura). This is obtained from several trees from Japan and Borneo. It is met with in solid, colourless, translucent, crystalline masses, usually covered with minute fissures ; it is very tough, but can be powdered by moistening with water, alcohol, or ether. It has a peculiar smell and hot, bitter taste. It is soluble 01 per cent, in water, 120 per cent, in alcohol, and also in ether and most oils. It is used in the preparation of celluloid, varnishes, and as an antiseptic.
Canada Balsam (Ger., Canadabalsam ; Fr., Baume du Canada; kal.. Balsamo del Canada). Synonym : Canada Turpentine. A pale greenish and faintly yellow turpentine obtained from various species of pine trees. It has the consistence of honey, and a pleasant resinous odour. It slowly dries by exposure to the air into a transparent adhesive varnish. Insoluble in water, soluble in all proportions in alcohol. It is used for making varnishes, and for cementing lenses together. (See Balsaming, Re-, of Lenses.)