VOL. XXVI.J PHILOSOPHICAL TRANSACTIONS. 38^ 



termined ; but he conjectured from some experiments, that the case stood ac- 

 cording to those made by the academy del Cimento. From these observations 

 it plainly appears, that sound may be heard at a much greater distance in Italy, 

 than Mr. Townley would have it; and I cannot help thinking, that sound is 

 propagated as freely in southern, as in northern climates; though there are not 

 wanting instances of the 'more considerable progressive motion of sound in som6 

 northern parts of the globe. For a certain Danish gentleman assures me, he 

 heard distinctly the firing of the guns of Carlescroon, at 80 English miles 

 distance; and Dr. Hearn informed the Royal Society, that the firing of the 

 guns at Stockholm was heard at the distance of 30 Swedish miles, which are 

 almost equal to 180 English; and in the naval engagement, A. D. 16/2, be- 

 tween the English and the Dutch, the report of their guns was heard upwards 

 of 200 miles off, even as far as Shrewsbury and Wales 



As to what the two Mr. Townleys have observed, it seems to be peculiar to 

 the castle of St. Angelo, or at least to Rome; and that diminution of sound, 

 which they observed, might be owing either to the situation of the castle, or to 

 the intermediate houses in that vastly large city; or to the several reflections of 

 the sound, or to contrary winds, or in fine, to some such similar cause: or per- 

 haps these gentlemen made the above observations, when the air was in such a 

 state, that though the sound had the most favourable wind to concur with it, 

 yet it was much more languid than at other times, when the wind is entirely 

 against it: and formerly I was of opinion, that there was always the same 

 temperament of air at Rome, though not in the other parts of Italy, till I read 

 Kircher's opinion, viz. that at Rome, which is surprising, the echo or sound 

 acquires great strength with a northerly wind ; grows languid with a southerly 

 wind ; and is in a mean state between both with an easterly, and an east-south- 

 east wind. 



^ 10. Of the various Remissness and Intenseness, or Audibility of Sound, accord- 

 ing to the different States of the Atmosphere. — I have often observed that sound 

 had an exceedingly languid motion in summer, when the air was warm ; but at 

 other times, especially in the winter, if it happened to freeze, it was much 

 more acute and strong. I also found that sound is more clear and shrill with a 

 northerly or easterly wind, however contrary, than if it blow from opposite 

 points, as Kircher likewise observed at Rome; though this is not a constant 

 rule. Nor could I determine any thing with more certainty, as from the ascent 

 or descent of the mercury in the barometer; for I observed the sound to be 

 sometimes most clear and shrill, and at other times most weak and languid, 

 when it rose the highest ; and on the contrary, when it was lowest have found 

 the sound sometimes very shrill and at other times very weak. And the case 



