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66. 

The only reliable procedure would be to send the smallest mass of flash powder possible to the dark surface of the moon when in conjunction (i.e., the "new" moon), in such a way that it would be ignited on impact. The light would then be visible in a powerful telescope. Further, the larger the aperture of the telescope, the greater would be the ease of seeing the flash, from the fact that a telescope enhances the brightness of point sources, and dims a faint background.

An experiment was performed to find the minimum mass of flash power that should be visible at any particular distance. In order to reproduce, approximately, the conditions that would obtain at the surface of the moon, the flash powder was placed in small capsules, [[underlined]] C [[/underlined]] Fig. 23, held in glass tubes, [[underlined]] T [[/underlined]], closed by rubber stoppers. The tubes were exhausted to a pressure of from 3 to 10 cm. of mercury, and sealed; the stoppers being painted with wax, to preserve the vacuum. Two shellacked wires, passing to the powder, permitted firing of the powder by an automobile spark coil.

It was found that Victor Flash Powder was slightly superior to a mixture of powdered magnesium and sodium nitrate, in atomic proportions; and much superior to a mixture of powdered magnesium and potassium chlorate, also in atomic proportions. 

In the actual test, six samples of Victor flash powder, varying in weight from 0.05 gram to 0.0029 gram were placed in tubes as shown in Fig. 23, and these tubes were fastened in blackened compartments of a box, Figs. 24 and 25. The ignition system was placed in the back of the same box, as shown in Fig. 26. This system comprised a spark coil, operated by three triple cells of "Ever-ready" battery, placed two by two in parallel. The charge was fired on