Those who depend upon daylight, especially dwellers in London, or other large cities and towns, have many a day of disappointed hopes. But they need not despair, for enlargements can be taken during the dullest days, or at night by means of the apparatus shown at page 126. This is virtually a magic lantern with an extended front. It is fitted with a patent light, giving a wonderful amount of illumination.
The secret of getting the greatest efficiency from any illuminant, the electric light excepted, is to furnish it with plenty of oxygen. Pure oxygen is out of the question, unless we are prepared to undertake all the trouble involved in using a lime light. But as ordinary air consists one-fifth of the gas, and as it can be had free of cost, it answers every purpose. To increase the flame of the fire the housemaid uses a pair of bellows. By the same law a conflagration becomes more brilliant in a high wind. Applying the same principle to the lantern (and it may be a lantern for exhibition purposes, or an enlarging lantern) the inventor of this special form of lamp employs a fan worked by clockwork in the body of the lantern itself. This fan delivers a constant and regular supply of fresh air, which plays in and around the wicks, adding much to the brilliancy of the light, and at the same time acting as a ventilator, and keeping the lantern cool. The increase of light power is enormous, and as it is a firmly established law, that the size of a picture shown by a lantern is only limited by the amount of illumination available, this increase is of the very first importance. The clockwork which drives the fan requires winding up once or twice during an evenings work with the instrument, an operation as noiseless and easy as the winding of a watch. This application of an old principle to the lantern is entirely new.
In using the enlarging apparatus with this artificial light, the front lens is used as an objective, and casts the enlarged image on a wall or screen. Upon this screen is fixed the sensitve paper, and the light given is so great that a quarter plate negative can be enlarged to 15 x 12 in about 3 minutes.