IV. ANEMOMETERS. 579 



glass tubes in *uch a way that the cross can partially rotate in a vertical plane. 

 The lower end of the bar carrying the board is counterpoised, so as to keep 

 the surface of the board vertical, and a scale pan, hung to one end of the 

 horizontal bar of the cross, serves to receive the weights, which are necessary 

 to counterbalance the force of the wind, pressing on the board opposed to it, 

 at any time. A small box, covering the scale pan; serves to shield it from 

 the action of the wind. The instrument was, at the time of observation, 

 placed so that the surface of the pressure plate should stand at right angles 

 with the direction of the wind, as indicated by a vane. 



2 84 la. Anemometer, large. L. Casella. 



2842. Electrical Anemometer, by which the velocity of the 

 wind in miles, &c., can be shown on dials in an observatory or 

 study. Yeates $ Sons. 



2843. Robinson's Anemometer, for measuring the wind's 

 velocity reading from -fa up to 1 ,000 miles-. Francis Pastorelli. 



This instrument consists of four hemispherical cups fixed to four strong 

 metal arms, that radiate from a central boss at a distance of 90 apart ; at right 

 angles to the plane of the cups is attached the vertical axis, its lower end 

 terminates with an endless screw ; this works two wheels which differ in the 

 number of teeth, so that by their common revolution one has 100 times less 

 velocity than the other. 



The front wheel has two divided circles, the interior denoting 10 miles ; 

 each mile is figured and sub-divided into 10 parts ; the outer circle is divided 

 into 100 parts ; each of these divisions represent 10 miles, every fifth division 

 50 miles, and they are numbered 50, 100, &c. ; therefore readings from J- U p 

 to- 1,000 miles can be taken by this instrument. 



2844. F. Fastorelli's Electric Anemometer, to indicate 

 from ^5- up to 10,000 miles. By the use of this instrument the 

 velocity of ths wind at any distant station may be seen by inspec- 

 tion in the observatory. Francis Pastorelli. 



It consists: (1.) of Dr. Robinson's cup arrangement attached to a vertical 

 axis ; as it revolves the motion is conveyed by its endless screw to a wheel 

 with a cam mounted in a rectangular metal box ; here the angular velocity is 

 reduced, so that each contact has the value of ^ of a mile ; (2.) the receiving 

 instrument with its dial is mounted in a polished cabinet ; it is worked by an 

 electro-magnet and lever, so when the revolutions of the cups have indi- 

 cated -J^ of a mile, the action of the lever works a wheel, and motion is 

 communicated to a series. On the face of the instrument are divided circles 

 and indexes which register from -^ to to 10,000 miles of velocity. (3.) A 

 Leclauche battery of four No. 2 cells is connected with the above, so that 

 each -J^ of a mile, indicated by the revolutions of the cups, may be trans- 

 mitted electrically and consecutively to the receiving instrument. 



This instrument has the minimum amount of friction. The cup arrange- 

 ment can be placed in any distant and convenient position, and the receiving 

 instrument in the observatory. It is portable, being of small dimensions. 



2845. New Portable Anemometer, by Francis Pastorelli, 

 for measuring accurately the velocity of the air or wind, specially 

 adapted for scientific travellers and explorers. Francis Pastorelli. 



Oo 2 



