(2) Work without condensers. Then, again, we may use petro-leum, gas, enriched gas, limelight, or magnesium; these, however, will be described as we go on.
(1) Solar Work. By this term we understand the use of the solar rays themselves, and not their light reflected from any card or white surface. Although this was one of the first processes employed before bromide paper was invented, and was used for printing on ordinary silver paper,' carbon tissue, etc., we shall dismiss this in a few words, because the apparatus is costly, and sunlight, unfortunately, not always available in our climate. For this work Woodward invented his solar camera, and Monckhoven improved upon this with his dialytic apparatus, other instruments also being made for the same purpose. Large condensers are absolutely necessary, not less than nine inches in diameter, and the solar rays have either to be kept motionless by means of a heliostat, or mirror mounted equatorially and driven by clockwork, or else by careful and attentive work of an operator. As, however, equally good results can be obtained by using the apparatus described hereafter, no further description will be given ; but, for the information of those desirous of spending their money, full and complete instructions will be found in Monckhoven's " Optics."
(2) Enlarging by Diffused Daylight. By many this will be found the most convenient and cheapest method of making enlargements ; but as to whether it is the best is altogether another question, which we shall consider later on at the end of the instructions for both methods of illumination. We have here also what may be practically considered as two distinct methods of working, the one using the actual light of the sky itself, and the other using reflected skylight. Before entering into particulars of either method, however, there are one or two details which it is advisable to elucidate. We may decide to use a darkened room or a special camera for the purpose of obtaining the enlargement, and the necessary arrangements will now be described. If we desire to use a darkened room, such as an ordinary sitting-room, it is obviously necessary that the light shall be prevented from having access to it by some means or other; therefore we will suppose that the room has one window,