Owing to the extremely feeble actinic force of moonlight, it is impossible to obtain instantaneous views by its aid, and a fully-exposed negative can be obtained only by large apertures of lenses of great luminous power, and by long exposure upon highly sensitive plates.

The first moonlit picture exhibited publicly was at the Exhibition of 1851. On account of technical difficulties resulting from long exposures on wet collodion plates, the attempts made then were but rarely successful, and only after the introduction of collodion dry plates were more satisfactory moonlight pictures really possible.

Burton states positively that to photograph a landscape illuminated by moonlight requires from 300,000 to 3,000,000 times longer than the same landscape illuminated by sunlight. . Von Gotthardt endorses what Burton says, and speaks of these facts more definitely when describing some experiments he made.

Eder speaks of an experiment by which he found the intensity of moonlight to be 6000 times weaker than that of a magnesium wire burnt in the focus of a concave mirror, and states, further, that he had made a moonlight landscape by an exposure of 3 hours upon a plate 20° Warnerke, with a Steinheil aplanate, stop f/10.

Henderson, under conditions similar to those of Eder, exposed for 7 hours, and Jahr had perfect negatives in 8 and 9 hours.

Dunmore obtained a very rich and harmonious moonlight landscape in 5 hours, and it is said that Colard and Holmer had the same results in 1-2 hours, while Causson and Co. exposed for 30 minutes with the full aperture of a portrait lens. The great difference of the times of exposure stated is owing mainly to the different forms of the objectives employed and their focal length, but is not at all contradictory to the principle laid down by Yon Gotthardt. Causson and Co. used a portrait lens, and Jahr a Dallmeyer rectilinear, both with perfect success, it is said.

For scientific purposes, and as a technical object lesson to the photographer, the attempts at making pictures by moonlight are very instructive perhaps, and are otherwise interesting; but artistically they do not amount to much. Light and shade are not distinctly defined, as the motion of the moon obliterates all artistic effect in the prolonged exposure, and the finished picture reminds one of the works of Chinese artists, totally devoid of details, as well as of light and shade.

Moonlight photographs with distinctly pronounced shadows are impossible, and those claiming to be so are invariably made by daylight produced by a variety of clever printing and other dodges, and may be very beautiful so far as the moonlight effect is concerned. - (Photo. Times.)