104 KEGRETTI AND ZAMBEA, HOLEOBN YIADUCT, E.G., 



FIG. 114. 



144. Robinson's Anemometer. Dr. Robinson, of Armagh, is the inventor 

 of this very useful anemometer, for determining the horizontal velocity of the 

 wind. It was first used in 1850, in the meteorological and tidal observations 

 made on the coast of Ireland under the direction of the Rev. Dr. Lloyd. It is 

 represented in its simplest form by fig 114. Four hollow hemispherical cups 

 AA, are extended upon strong metal arms, with their concave services facing 

 the same way upon a vertical axis, B, which has at its lower extremity an end- 

 less screw, D. The axis is supported and strengthened at (7, and constructed 

 so as turn with as little friction as possible. The endless screw on the vertical 

 shaft is placed in gear with a train of wheels and pinions. Each wheel revolves 

 past a fixed index, and the figures and graduations are marked upon the wheels 

 themselves. 



The readings on the dials of the Anemometer are as follows : one complete 

 revolution of ihe first engraved index- wheel equals -^ of a mile; the second, I 

 mile ; the third, 10 miles ; the fourth, 100 miles ; the fifth 1,000 miles ; neces- 

 sarily in noting such reading it must be done backwards, according to the 

 indications on the instrument. 



Dr. Robinson has proved by theory and experiment that the centre of any 

 one of the cups mounted as fig. 114 revolves with one-third of the wind's 

 velocity. Therefore allowance has been made for this in graduating the circles, 

 and a true reading is at once obtained. Price, fig. 114 3 3 and 440 



145. Robinson's Anemometer. Negretti and Zambra's improved 

 arrangement for recording the velocity of the wind, as described by Colonel Sir 

 H. James, Royal Engineers. This is a modified form of the Robinson 

 instrument previously described, our engraving (fig. 115) will show the general 

 details of the mechanism. 



. It consists of four arms at the end of which there are four light hemis- 

 pherical hollow metal cups, the concave surfaces facing in one direction and 

 revolving with one-third of the velocity of the current of wind acting on them. 

 On the vertical axis which carries the arms, there is an endless screw, which 

 communicates its real velocity of rotation to a circular dial. 



