Page:Popular Science Monthly Volume 6.djvu/714

694 was heard striking loudly eleven. Toward evening this fog began to melt away, and at six o'clock I went to the end of the Serpentine to observe the effect of the optical clearing upon the sound. Not one of the strokes reached me. At nine o'clock and at ten o'clock my assistant was in the same position, and on both occasions he failed to hear a single stroke of the bell. It was a case precisely similar to that of December 13th, when the dissolution of the fog was accompanied by a decided acoustic thickening of the air.

—Satisfactory and indeed conclusive as these results seemed, I desired exceedingly to confirm them by experiments with the instruments actually employed at the South Foreland. On the 10th of February I had the gratification of receiving the following note and inclosure from the deputy-master of Trinity House:

The inclosure referred to was notes from Captain Atkins and Mr. Edwards. Captain Atkins writes thus:

"However, had I been on board, the instructions I left with Troughton (the master of the Argus) could not have been better carried out. About noon the fog cleared up and the Argus returned to her moorings, when I learned that they had taken both siren and horn sounds to a distance of 11 miles from the station, where they dropped a buoy. This I know to be correct, as I have this morning recovered the buoy, and the distances both in and out agree with Troughton's statement. I have also been to the Varne light-ship (12$3/4$ miles from the Foreland), and ascertained that during the fog of Saturday forenoon they 'distinctly' heard the sounds."

Mr. Edwards, who was constantly at my side during our summer and autumn observations, and who is thoroughly competent to form a comparative estimate of the strength of the sounds, states that the sounds were "extraordinarily loud," both Captain Atkins and himself