Page 41 - January 2009

[a SW by W would indicate a wind directly from Blackheath to Derham’s observation point.
b The wind velocity is indicated by the number given after the direction. See text, Sections 11 and 12.
c Customary usage of the year included January and February following. For example, Feb. 13 is listed above under the heading, 1704. The
next entry is Mar. 30 under the heading, 1705, but these two observations are most likely only a few weeks apart rather than a full year apart (and both would be in 1705 by modern accounting).]
motion of the wind and of the sound was nearly coincident, and when the same wind was a little stronger (as is denoted by the number 7 annexed, just as the number 0 denotes tran- quil weather, and as the numbers 1, 2, 3, 4, signify different powers of the wind) then, I say, the sound finished its passage in the space of 111 half seconds. But on the 24th, when the wind was blowing from the same quarter, and the air was still, the sound made the same passage in an interval of 116 half seconds. So likewise on the 7th of February, 1706 when the wind was blowing from the same quarter of the compass and was carrying the sound with it, but now with only half the strength, 113 half seconds elapsed before the sound made its
ty respecting all these things I will subjoin in the following table certain special observations, which were made after I had before noted that the cannon on the Blackheath grounds ranges from the sound, that is, that they inclined to the quar- ter of the compass a little beyond S.W. by W.
I have selected these observations from very many oth- ers, all of them being cautiously made and each one repeated two or three times or oftener, so that what I have said above respecting their truth is abundantly and indubitably mani- fest. For, from the experiments made on April 5 and Sept. 29 it is plain that the stronger winds push forward and hasten the velocity of sounds. For on the fifth of April, when the
40 Acoustics Today, January 2009