VOL. LVI.J PHILOSOPHICAL TRANSACTIONS. 339 



pass over the same space which they had moved over in 1 5 seconds, in the former 



trials. 



Feet 

 This space measures exactly 1384= space passed over in 15 seconds, 

 which multiplied by 4 



gives 5536=space passed over in one minute, 

 which multiplied by 60 



gives 332,l60=space passed over in one hour. 



Which space is =62.9 English miles per hour, the velocity of the wind in 

 March 1763. One-third of this, or '21 miles nearly, shows the velocity of the 

 wind on May the 6th, when it blew a fresh gale. May 12, there was a small 

 westerly breeze, the velocity of which he measured on the same line, the sun 

 being 10 minutes past the meridian, and found that the shadow took 95 seconds 

 to pass over the above space ; which gives the velocity of the wind at the rate of 

 9.9 English miles per hour. 



Thus, by having several lines in different directions of a known length marked 

 on the ground, one may easily, and with great accuracy, measure the velocity of 

 the wind. If a person was provided with an instrument for measuring the force 

 of the wind, it would perhaps be worth while to observe whether, when the ve- 

 locities of different winds were the same, or nearly so, the forces of these winds 

 did not vary with the seasons of the year, the points of the compass from which 

 the wind blows, and also with the different state of the barometer and thermo- 

 meter, since the momentum of the wind depends not only on its velocity, but 

 also on its density. 



From the end of March 1 7 65, to the end of March last, in that part of Scot- 

 land, they had very little rain, and less snow in proportion ; the rivers were as 

 low, through the winter, as they used to be in the middle of summer ; springs 

 failed in most places, and brewers and maltsters were obliged, even in winter, to 

 carry their water from a considerable distance. 



In the end of March last, they had a fall of snow ; and, as he did not remem- 

 ber to have ever read an account of such an experiment, he wished to be able to 

 determine, to what quantity of rain this fall of snow was equal. The snow had 

 been falling from 5 o'clock the former evening, till 10 o'clock next day ; about 

 11 o'clock he measured the depth of the snow, and found it to be 6.2 inches; he 

 then took a stone jug, holding about 3 English pints, and turned the mouth of 

 it downwards on the snow measured, and where the ground below was smooth, 

 and hard ; and by this means he took up all the snow from top to bottom in the 

 jug ; this snow he melted by the side of a fire, and the 6.2 inches of snow 

 yielded 6 tenths of an inch deep of water in the same jug. After emptying the 

 jug, he dried, and weighed it in a balance, and took up the same quantity of snow 

 in it as before, weighed it again, and found the weight of the snow taken up, and 

 from this weight computed what quantity of water it should have produced, and 



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