Page:Popular Science Monthly Volume 13.djvu/299

Rh still superior to the gun. On the 6th of August, at St. Ann's, the 4 ounce and 8-ounce rockets proved superior to the siren. On the Shambles Light-vessel, when a pressure of 13 pounds was employed to sound the siren, the rockets proved greatly superior to that instrument. Proceeding along the sea-margin at Flamborough Head, Mr. Edwards states that at a distance of 1 mile, with the 18-pounder gun hidden behind the cliffs, its report was quite unheard, while the 4-ounce rocket, rising to an elevation which brought it clearly into view, yielded a powerful sound in the face of an opposing wind.

On the evening of February 9, 1877, a remarkable series of experiments was made by Mr. Prentice, at Stowmarket, with the gun-cotton rocket. From the report with which he has kindly furnished me I extract the following particulars. The first column in the annexed statement contains the name of the place of observation, the second its distance from the firing-point, and the third the result observed:

In the great majority of these cases, the direction of the sound inclosed a large angle with the direction of the wind. In some cases, indeed, the two directions were at right angles to each other. It is needless to dwell for a moment on the advantage of a signal commanding ranges such as these.

The explosion of substances in the air, after having been carried to a considerable elevation by rockets, is a familiar performance. In 1873 the Board of Trade actually proposed a light-and-sound rocket as a signal of distress, which proposal was subsequently realized, but in a form too elaborate and expensive for practical use. The idea of the gun-cotton rocket with a view to signaling in fogs is, I believe, wholly due to