Scientific men have often to perform elaborate experiments for small results, but in the present case the question at issue was both interesting and instructive. Being desirous of testing the velocity of sound between two places of different heights above the sea-level, two Frenchmen arranged for a small brass cannon to be fired from the top of a mountain in Switzerland (Faulhorn), and another from a little village near Lake Brienz, 6500 feet lower than the former spot. The cannon—which were those used by the homely villagers in their festivals—were discharged twenty-eight times, and it was found that though the speed of the sound was not affected by the height, there was a very decided difference in the strength.

The report from the cannon at the lake was well heard on the mountain-top, while that from the latter was feeble, the strength of the sound being found to depend partly upon the density of the air at the place of its production, and not at the place of its being heard.

Thus, in order to produce a sound whose intensity should be the same at both spots, it was necessary to put eight parts of powder in the cannon on the mountain for every seven used in the charge for the gun by the lake.