METEOROLOGY. 319 



meter, upon which is clamped a paper registerJ(old newspapers answer 

 very well) washed over with whiting and flour paste. Upon the 

 surface of this register is traced by a pencil the direction of the wind ; 

 this register is renewed every twelve hours. 



The velocity shaft is in two pieces, connected by means of the toothed 

 wheels and steel pivots, as in the direction shaft ; and, practically, 

 the friction is nil. At the top of the velocity shaft is fixed three 

 hemispherical tin or copper caps, 10 inches in diameter, similar in 

 construction to those of the Rev. Dr. Robinson's, of Armagh, and are 

 firmly riveted to three iron arms of -|-inch iron. These caps revolve 

 always in the same direction, and one revolution is found to be just 

 one-third of the linear velocity of the wind. I have no reason to 

 doubt Dr. Robinson's formula for this calculation. At the lower ex- 

 tremity of the velocity shaft is fixed a one-toothed wheel 2f inches 

 in diameter ; this moves a second, or ten-toothed, wheel, which also 

 gives movement to a tliird wheel, which marks a hundred revolutions 

 of the caps, which are so calculated that each one hundred revolutions 

 are equal to one mile linear, and whenever one hundred revolutions 

 have been accomplished a small lever is elevated by means of a small 

 inclined plane, which is fixed upon the edge of the last wheel, and 

 which gives motion to the level. The other extremity of the lever is 

 furnished with a fine steel point, which dots oflF, upon a paper register, 

 the miles as they pass. This register is of paper one and a quarter 

 inch wide, and is removed every twelve hours. 



Between the two shafts at the lower extremities is placed two run- 

 ners of wood rebated to receive a slide or train which carries the register. 

 To the underside of this slide is fixed a rack and is moved by a pinion, 

 themovement of whichiscommunicatedby aclock,thecordof the weight 

 being passed over a wheel and pulley and advances one inch per hour, 

 and the lever before described dots off the miles as the register ad- 

 vances under the steel point ; it does in this manner show the increase 

 and decrease of the velocity, and also the moment of its change. At- 

 tached to this moveable train is a rod of wood carrying a pencil, which 

 passes over the disc connected with the direction nhaft, and there 

 traces, as it advances, the direction of the wind a-j i the moment of 

 its changes, and the point from which it veered. T ; extreme height 

 of the vane is 40 feet, which might be increased i required. The 

 clock is wound up every twelve hours, which bring • back the train to 

 its starting point. 



There is also a polariscope and prism for experimenting on the 

 various rays of light in connexion with photography and the germi- 

 nation of seeds. 



The observatory also possesses a quadrant and artificial horizon, 

 and also apparatus for the measure of haloes, and registering dial for 

 the direction and course of the clouds. 



