METEOROLOGICAL INSTRUMENTS. 



37 



Fig. 8. 



Fig. 9. 



rounded by a second tube or steam jacket. The 

 inner tube has perforations near the top which 

 allow the steam readily to fill the intermediate 

 e and freely to escape by a side tube, as 

 shown in the figure. The thermometer is 

 ported, at about one inch above the surface of 

 the water in the boiler, by means of a cork or 

 India-rubber washer on the upper part of the 

 stem, and can be immersed in the steam to any 

 required amount by sliding the telescope tube 

 to any required height. Distilled water is 

 used in this instrument, which is made to boil 

 by means of a spirit lamp. The whole is 

 packed in a leathern sling case, shown in Fig. 9. 

 rig. to. 



1 



f 



Fig. 10 represents a portable anemometer for 

 registering the velocity of the wind in miles and 

 furlongs. 



This instrument is a modification of the anemo- 

 ) meter devised by Dr. Robinson, of Armagh, which 

 consists essentially of four hemispherical cups, hav- 

 ing their diametrical planes exposed to a passing- 

 current of air; they are carried by four folding 

 horizontal arms attached to a vertical shaft or axis. 

 which is caused to rotate by the motion of the 

 wind. Dr. Robinson found that the cups, and consequently the axis 

 to which they are attached, revolve with one-third of the wind' s 



