The Rev. H. Lloyd on the Meteorology of Ireland. 445 



We see that the terms of the estimated scale correspond, nearly, to an 

 arithmetical progression oi velocities, and not oi pressures. This fact has been 

 already noticed by Dr. Robinson. 



The common difference in this series, which is equal to its first term, is 

 obtained from the numbers of the third column by means of the formula 

 F= nT^i. The following are the deduced values : — 



I. F, = 120 IV. Fi = 10-8 



II. 12-5 V. 10-2 



III. 11-7 VI. 12-5 



The mean of these values is V, = 11 '6. The calculated values of V, con- 

 tained in the last column of the foregoing Table, are, accordingly, obtained from 



the formula 



V=n-&xn; 



their agreement with the observed values is sufficient to establish the assumed 

 law. 



As a verification of the preceding result, I took also a tolerably extended 

 series of measurements oi the pressures of the wind, corresponding to the highest 

 term of the scale, with Lind's anemometer. Their mean gave 2-06 inches for 

 the reading of the instrument corresponding to that term ; and the corre- 

 sponding pressure on one square foot of surface, computed in the proportion of 

 5-20 pounds to the inch, is 10'7 pounds. Hence, the pressure belonging to 

 the unit of the scale is P, = 0'30. The corresponding velocity is inferred from 

 the formula V- = 437 P. Its value is Fi = 11"5; a result which agrees very 

 closely with that already deduced from Robinson's anemometer. 



The results hitherto given rest only on my own estimations ; it remains 



the instrument accordingly provided with a little hammer, which is pressed against the regis- 

 tering wheel by a spring, and which, being raised by a projecting pin at one point of its circum- 

 ference, falls again with a sharp noise when this has passed. The interval between two such 

 strokes of the hammer, therefore, is the time of one whole revolution of the registering wheel, or of 

 100 revojutions of the arms. Accordingly, a chronometer being held close to the ear, the whole 

 observation is effected by the help of that organ. The velocity of the wind in this case is given 



ftfi4 

 by the formula F= -=^, jT being the observed time of 100 revolutions. 



3 M 2 



