252 



REPORT 1844. 



In a similar way one-half the velocities of south-west and south-east winds 

 are taken and added to the velocities of the intermediate points, calling the 

 whole souths and so on, according to the following formulae: — 



^^•-fN.N.W. + N. + N.N.E. + ^'=N. 



^•-fS.S.W. + S. + S.S.E. + ^ 



= S. 



2i:£•-fE.N.E.-^E.^-E.S.E. + — =E. 

 2 2 



^il^--|- W.N.W. + W.4- W.S.W. + ?^=W. 

 2 2 



Substituting the arithmetical quantities in Table A in these formulae, we 

 have N. = 12852, S. = 8959, E. = 6276, W. = 39598. Subtracting S. 

 from N. and E. from W., we have the two rectangular forces, N = 3893, 

 and W. — 2>i2i'2,\, the resultant and direction of which will be as in the an- 

 nexed figure. Magnitude of resultant = a/ 33321 2+ 38932 = 33547. Di- 



viding by 8760, the total number of hours in the years, gives about 3*8 miles 

 per hour. The direction of the wind therefore in the locality of this instru- 

 ment, from November 1843 to November 1844', would be about W.N.W. to 

 E.S.E. with a velocity of 3'8 miles per hour, being a velocity the same as 

 that obtained by Professor Whewell's instrument. 



The Right Honourable the Earl of Burlington, one of the late Presidents 

 of the British Association, has been so good as to place in my hands some 

 manuscripts found amongst the papers of the late Mr. Cavendish, and con- 

 taining no doubt the results of valuable experiments on revolving vanes, 

 which would be likely to throw some further light on the working of such 

 instruments as this; but from the absence of all information relative to these 

 experiments, it is impossible to come to any satisfactory conclusions relative 

 to them. Mr. Cavendish, who left few inquiries in experimental science un- 

 touched by his powerful hand, had evidently considered the subject of re- 

 volving vanes as a means of determining the velocity of the wind. His ex- 

 periments were made on machines of considerable magnitude, the arms on 

 which the vanes were fixed being nearly ten feet long, the total diameter of 

 the fly therefore was twenty feet ; the motion of this fly appears to have been 



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