flame from gas thus enriched ought to yield a light of great excellence, provided it has a smaller flame ascending through its centre, and that provision is made to condense it by diminish-ing its diameter, either by a brass solar cap to cause a strong current of air to impinge upon the flame a little above the burner, or by a contraction in the glass chimney. Whiteness and intensity in such a case are increased by a judicious lengthen-ing of the chimney to increase the draught. The area of the flame must, however, be reduced by the expedient already pointed out." The Welsbach or Incandescent gas burner is one par-ticularly adapted for enlarging, as the light emitted is exception-ally rich in actinic rays, and the exposure thereby considerably shortened. In some experiments in connection with this light we found that with the ordinary household gas supply the exposure was cut down to one-quarter of that with an ordinary three-wick lamp.
Limelight This is, of course, one of the most convenient of all sources of light, and is so well known as to need but little description.
Magnesium. So far as we know there is no commercial apparatus for utilising magnesium as an illuminant with con-densers, though of course it would be quite possible to utilise any ordinary enlarging lantern with a clockwork arrangement for feeding the magnesium to a small spirit flame, so as to keep the radiant point at one particular distance from the condensers.
The Electric Light. Few amateurs, or even professionals, can afford the necessary outlay for this light, the cost of even a primary battery or accumulators being considerable. In many parts of London, however, the wires for electric lighting are now laid along the principal thoroughfares, and it is easy to connect. The apparatus for enlarging by artificial light bears some resemblance to the ordinary or so-called magic-lantern. It is immaterial of what nature or substance the body of the lantern is, provided it be light-tight and strong. Russian or sheet-iron, copper, or wood with metal lining - all are used by commercial firms. The enlarging apparatus practically consists of a camera attached to an optical lantern, focussing being effected by rack and pinion. We need make no further mention of these, except that we shall later give a sketch showing how an ordinary magic-lantern may be adapted for enlarging.