Robinson — On the Cup Anemometer. 



429 



Name of Maker. 



a. Kil. 



b 



Length of 

 radius. 



Diameter. 



Browning, .... 



3-66 



1-iin 



11-99 



5-84 



Casella, 317 . . . 



2-o6 



2-7548 



6-75 



3-015 



CaseUa, 318 . . . 



1-90 



2-8472 



6'7S 



3-015 



Nowikoff, .... 



1-81 



2-8979 



8-61 



3-77 



No. 4, 



2-49 



2-5293 



4-85 



4-11 



He gives also the result of a trial to detennine the constants for 

 Browning by cariying it on the tender of a locomotive to and from 

 Zarsko-Selo, a distance of 19 versts = 20-27 k. He gives the mean V 

 going 32-14 and returning 26-90; and v = 13-76 and 9-17. This 

 reference to hourly velocities rather masks the result, and it is sim- 

 pler to say that while the engine traversed 20-27, the Anemometer 

 showed 8-675 going and 6-837 returning. The difference is referred 

 to a Kght wind which blew. He endeavoured to estimate the effects 

 of this by means of an Anemometer Breguet fixed on the tower of 

 the Observatory ; but as this was 77 feet above the ground, and fi'om 

 4 to 25 k. from the rail, he attaches little importance to its data, 

 except inferring that the direction of the wind made a mean angle of 

 22° with that of the rail ; and comparing the F's going and coming, 

 he deduces for the mean velocity of the wind along the rail (3y his 

 formula, first assuming a = 1 and then 3) 2-8 ; (Breguet woidd give 5-2). 

 From these he finds for Browning « = 3-11 ; )) = 2-3091. 



Lastly, he placed the two Casellas and Browning on the Observatory 

 tower, where two others were permanently established. But, as the 

 platform was only 10 feet 5 inches square, they must have been too 

 close to act freely. However, he got by his equations very nearly 

 accordant results for the three.* The remainder of the paper is occu- 



* Similar but more extensive experiments were made by tbe Rev. Fenwick 

 Stow (" Meteorological Journal," vol. i.), of wbicb I learned the existence from 

 M. Dohrandt's paper. Six Anemometers of different types from tbe Kew one, 

 r = 24 incbes, d = ^ incbes, to Casella r = 6.7, d = 3.01, were establisbed on open 

 ground, and tbeir indications were taken dui-ing a considerable period, and with 

 values of F", as given by tbe Kew, ranging from 3"^ to 34™. He finds that instru- 

 ments witb sbort arms do not agree even approximately witb tbe Kew one, except 

 at low velocities ; tbat tbose wbicb bave tbe smaller cups relative to tbe arms, 

 maintain at all velocities a tolerably even percentage of Kew, and tbat, in ail 

 cases (supposing tbe F given by Kew to be tbat of tbe wind), they move moro 

 rapidly in proportion to tbe wind as V is smaller. This is in complete opposition 

 to Dohrandt's results, and (as will be seen) to theory. Comparing Casella and Mr. 



