45, COKNHILL, E.G., AND 122, EEGENT STREET, W., LONDON. 97 



FIG. 108. 



137. Wegretti and Zambra's Improved Pendulum Anemometer 

 invented by Dr. Prestel to exhibit at any moment in a most simple manner the 

 direction and comparative pressure of the wind. 



By the action of the peculiar shaped vane A, the surface of the swinging 

 pressure plate, B, is always kept facing the point from which the wind is 

 blowing, and consequently exposed to its influence. During a calm the 

 pendulous plate, B, will hang quite vertical in a line with the axis of the vane 

 plate indicating zero or calm. As the wind increases in force the pressure 

 indicator will be raised to various points between 1 and 10 of the vane. 



The holes are drilled through the plate of sufficient size to be plainly 

 visible at a considerable height from the ground ; and to facilitate the reading, 

 the 5 and 10 are of a larger conical form, so that the position of the pressure 

 plate can be quickly observed. 



The subjoined table gives in English and French measures the value of the 

 indications. The Metrical scale is calculated to show the pressure of wind in 

 kilogrammes on the square meter, and the English scale pounds on the square 



foot. 



I. II. 



