Velocity of Sound. 121 
range upon the barometric scale, all the other probable elements 
of modification remaining constant; then, through a sufficiently 
extensive range upon the thermometric scale, the others remaining 
invariable, and so on; the question would soon be set at rest: 
but this is impossible. It becomes desirable, therefore, to augment 
the number of recorded facts, as they result from accurate ex- 
periments, in order that, at some future (and it is hoped, no very 
remote) time, a cautious investigator may so select, compare, and 
classify them, as to deduce a more comprehensive and accurate 
theorem than is yet known. 
With a view to contribute, though in a small degree, to this 
purpose, I now present an account of a few experiments made by 
myself in the course of the present year. 
My objects were, to ascertain the velocity with which the sound 
passed over the surface of the earth, over the surface of water ; 
under different temperatures ; m a quiescent state of the atmosphere, 
and in windy weather; by day and by night; the velocities of 
direct and reflected sound ; and the velocities of sounds of different 
intensities and produced by different means. As yet the expe- 
riments have not been carried to their projected extent ; but while 
I record the results thus far obtained, I look forward with hope, 
that, in another year or two, I shall be able to complete them 
satisfactorily. 
The instrument with which I measured the intervals of time, 
was one invented and made by Mr. Hardy, by means of which, 
with a little previous practice, I could measure an interval accu- 
rately to a tenth of a second, and approximatively to a twentieth 
ofa second. The velecity of the wind was ascertained by means 
of an anemometer ; and the barometer and thermometer were of the 
best construction. 
I employed no hygrometer, (much as I wished it); for as yet, 
I am not acquainted with any in whose results I should be inclined 
Vol. \X. Part 1. Q 
