XII. On the Results of Observations made with a new Anemometer. By 

 the Rev. W. Whewell, M. A. Fellow and Tutor of Trinity College. 



[Read May \, 1837-] 



In the present paper I shall give an account of the mode which 

 has been employed in using an Anemometer which I have invented 

 and caused to be erected. By this account I hope to shew that such 

 instruments may be made to give consistent and comparable results, 

 and may lead to a more complete knowledge of the course of the 

 winds than we yet possess. 



It is not necessary to describe in detail the construction of the 

 instrument here spoken of; its general principles may be easily ex- 

 plained. A fly (resembling the fly of a revolving ventilator or the 

 sails of a windmill) is fixed to the small end of the vane of a weather- 

 cock, so as always to be turned with its circular disk to the wind ; 

 and it consequently revolves by the action of the wind with a rapidity 

 increasing as the strength of the wind increases. The revolutions of 

 the axis of this fly are converted, by a train of toothed wheels and 

 screws, into a vertical motion, by which a pencil is carried downwards 

 touching the surface of a vertical cylinder, the cylinder having the 

 axis of the weathercock for its axis. As the vertical rod on which 

 the pencil slides is attached to the vane of the weathercock, the ^jo?"w/ 

 of the compass from which the wind blows is recorded by the side of 

 the cylinder on which the mark is made, while the quantity of the 

 wind is represented by the extent of the descent of the pencil. 



In the instruments which I have had constructed, the pencil 

 descended one-twentieth of an inch for ten thousand revolutions of 

 the fly, and the cylinder on which the marks were made was sixteen 



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