[Illustration: 50. Branch-like arrangement of twigs and delicate fern-like leaves] It is only quite recently, in fact, that the beautiful etchings of Jack Frost have been classified and photographed in all their perfection. Happily this has now been accomplished, by the aid of a compound photographic camera, and it opens up a new and fascinating field to the camera expert as well as to the student of frost crystals. Marvellous indeed is the variety and detail displayed in these attractive window-pane etchings furnished by the Frost Spirit, and if one is housed some day, in mid-winter, zero weather, one may watch the entire growth and development of these exquisite frost etchings from start to finish. To do this, place a lamp or candle before a frost-covered window, in a cold room, or unheated by furnace, of course not near enough to the glass to crack it, but just close enough to melt the heavy frost curtain which may have formed previously upon the glass. After this has been allowed to dissolve gradually, you will observe a thin water film or formation which has been left upon the outer edge of the glass, the centre of which will be clear. Do not disturb this film, for it is in part from this that the frost crystallisations form and develop. As soon as you move the lamp away from the glass, the pictures instantly begin to grow and develop. Delicate, feathery etchings of ice crystals first appearing around the outer edge of the water film, and according to the temperature of the room, form rapidly or slowly. Exquisite tracings, and fern-like leaves shoot out as by magic toward the centre of the glass, but as soon as they reach a dry place upon the glass, they instantly cease. If you observe very closely, you will discover that meanwhile, in the little open spaces, between the bolder fern-like designs, more delicate feathery forms are gradually appearing, formations which sometimes resemble fine coral branches. As soon as the water-film ice crystallisations are completed they are closely followed by the true frost crystals, which form upon the various dry places upon the glass, delicate lines and stars and also in a thin, dew-like deposit, which rapidly freezes, and assumes a granular, snow-like form. This granular frost develops very rapidly, and soon covers all the unoccupied, clear, dry places; but one curious fact worthy of observation: it does not intrude upon, or approach near to the separate and individual designs or masterpieces, of the frost already formed upon the glass, but rather draws away from their immediate vicinity. This strange habit of the granular frost is well shown in the photographed illustration, where it will be observed that the granular frost acts merely as a background or sky effect for the real frost pictures, as in a painting. [Illustration: 51. Moss-like arrangement of frost] [Illustration: 52. Twin freaks]