Note cc — BOOK IV.

As to the Distance to which Sound may be sent, having some doubt, whether there was any Difference between the Northern and Southern Parts, by the Favour of my learned and illustrious Friend Sir Henry Newton, her Majesty’s late Envoy at Florence: I procured some Experiments to be made for me in Italy. His most Serene Highness the Great Duke, was pleased to order great Guns to be fir’d for this purpose at Florence, and Persons were appointed on purpose to observe them at Leghorne, which they compute is no less than 55 Miles in a strait Line. But notwithstanding the Country between being somewhat hilly and woody, and the Wind also was not favouring, only very calm and still, yet the Sound was plainly enough heard. And they tell me, that the Leghorne Guns are often heard 66 Miles off, at Porto Ferraio; that when the French bombarded Genoa, they heard it near Leghorne, 90 Miles distant: and in the Messina Insurrection, the Guns were heard from thence as far as Augusta and Syracuse, about 100 Italian Miles. These Distances being so considerable, give me Reason to suspect, that Sounds fly as far, or nearly as far in the Southern, as in the Northern Parts of the World, notwithstanding we have a few Instances of Sounds reaching farther Distances. As Dr. Hearn tells us of Guns fired at Stockholm in 1685, that were heard 180 English Miles. And in the Dutch War, 1672, the Guns were heard above 200 Miles. Vid. Phil. Trans. Nᵒ. 113. Also there is this farther Reason of Suspicion, that the Mercury in the Barometer riseth higher without than within the Tropicks, and the more Northerly, still the higher, which may encrease the Strength of Sounds, by Note (bb).