u 



house. One of the neatest instruments of this class was invented 

 by Dr. Schmidt of Giessen, in 1828. A rod ab which has a 



circular plate at its lower extremity, is pivoted at c about one-third 

 of the way down. As it swings back before the wind, its upper 

 end slides along a quadrant and pushes forward an index D, which 

 remains to show the maximum effect of the gusts. In order to 

 keep the plate face to the Mond, the rod is pivoted at c in a light 

 frame, wliich itself forms part of the spindle of a vane or weather- 

 cock, and turns with it. Another very pretty modification of the 

 same principle is that introduced by Mr. Howlett in 1868 : in this, 

 a sphere, about the size of a child's head, takes the place of the 

 plate, and is ready to catch the wind from whatever direction it 

 may come. This sphere is at the upper end of a rod which is 

 pivoted in the middle, on a imiversal joint, and bears a weight, as a 

 sort of counterpoise, at its lower extremity. As it swings with the 

 wind, a pencil traces the directions and extent of its motion on a 

 slate or card placed below. 



An instrument of this type is still used in Russia, for 

 measuring the force of the wind. In this country, however, they 

 have not been generally approved of, and the instrument by which 

 " pressure " is here more commonly measured- is a plate bearing 

 back on a spring, in the same way as the machines for trying " how 



