778 The Outline of Science 



7 



Wind Recording 



For obtaining records of wind force and direction the 

 standard instrument now employed is the Pressure Tube Anemo- 

 graph, invented by Mr. W. H. Dines, F.R.S. There are some 

 slight differences in detail in the more recent models, but all pat-, 

 terns work on the same general principle. A steel pole varying 

 in height between 15 and 80 feet, according to circumstances, car- 

 ries at its top a movable vane which is really an open tube, the 

 mouth of which always faces the wind. By means of a system of 

 connecting pipes the wind-pressure at the mouth of the vane is 

 transmitted to the recording part of the instrument. This consists 

 essentially of a hollow water-borne float to which a recording pen 

 is attached. The change of wind-pressure causes the float to rise 

 and fall, and so moves the pen over the chart. The pen pulses up 

 and down with every fluctuation of the wind, and the record 

 obtained shows a broad ribbon-like trace, the middle of which 

 gives the average velocity of the wind, while every single gust is 

 recorded. In gales the average wind velocity may be about 50 

 miles per hour, but the individual gusts may reach to over 80 

 miles, while the lulls may sink to about 20 miles. The highest 

 gust yet recorded in the country was of one of 110 miles per hour 

 at Quilty during the storm which swept northwards across Ireland 

 on 27th January, 1920. 



In addition to the velocity and gustiness of the wind, this 

 anemometer records also the direction from which the wind is 

 blowing. The movements of the vane are transmitted by an 

 attached rod, which passes through the hollow pole-support 

 directly down to the recording part, where the variations of 

 direction are traced on the same chart just below those of the 

 velocity. 



An older form of recorder, the Robinson Cup Anemometer, 

 gives a record only of the mileage run by the wind in an hour. The 



