Marten.—On Anemometry. 297 
cups and moderately short arms; No. 5, ditto, with arms only two inches 
in length; No. 6, ditto, with nine-inch arms; No. 7, ditto, but with 
eighteen inch arms and large elliptical cups; No. 8, ditto, but with very 
light tin cups and arms; No 9, ditto, but the cups conical instead of 
hemispherical ; and No. 10, a large standard anemometer, with copper cups 
nine inches in diameter, as recommended by Dr. Robinson. Omitting the 
intermediate results, which progress by tolerably uniform degrees from 
minimum to maximum difference, the respective results at the highest and 
lowest velocities observed were as follows :— 
Velocities 
Lowest|At Highest 'C/Oclties 
No. — A: Velocity rg 
: Miles. Miles. In Miles 
per Hour. 
1 | Casella's e A is ev * s 833 762 3—35 
2&3 An ond 8 ws E m ki s 1,041 748 3—38 
4 22 se ie 24 1,120 750 4—30 
5 í "Short arms . Ae Ef P g: 810 619 11—35 
6 » Long arms ae 856 822 . 7—40 
T » Longer arms and inre cups . 3 915 850 9—18 
8 » Light tin ¢ mph ave e 840 568 5—30 
9 a. T n. deep A none 661 —A41 
10 Kew standard, 9in. ined S 1,000 1,000 — 
On this discouraging result Mr. Stowe remarks,— 
“ It will at once be seen that the results of these experiments are, in the 
case of every instrument tried, utterly irreconcilable with Dr. Robinson’s 
dictum, that the centre of each cup travels at one-third of the rate at 
which the wind moves, and that this law is irrespective of the size of the 
cups or the length of the arms. Anemometers with short arms do not 
agree even approximately with the standard, excepting at low velocities : 
but there is this peculiarity, that, while those which have the smallest 
cups relatively to the length of arm, maintain at all velocities a tolerably 
even percentage of the motion of the standard, those on the contrary 
which have large cups and arms move at a high relative speed in very 
light airs, but fall actually below the others when the wind is high. If 
the standard be assumed correct, the cups of most of the small instru- 
ments move through a space scarcely more than one-fourth of that passed 
over by the wind. Of course it may be asked—which is correct? I do 
not know with what instruments Dr. Robinson’s experiments were made ; 
but I assume that, as he adopted and recommended the adoption of large 
anemometers, they ought to be taken as a standard, at least till they are 
proved incorrect, about the probability of which even I have no means of 
forming an opinion. Only as our confidence has been rather rudely shaken 
in one respect, we, perhaps, need re-assuring that the relation between the 
wind and the cups is not equally mythical.” ul 
