80 SEC. 3. MEASUREMENT. 



It consists of a broad brass ring ; fixed to it is a metal frame which carries 

 three divided circles ; in the interior and centre of the ring is a spindle 

 which carries eight vanes ; on one end is an endless screw ; this works a series 

 of wheels, which give motion to the hands on the dials, which record the 

 velocity of the air current every foot up to 100, 1,000 and 10,000 feet. 



410g. Dickinson's Anemometer. 



Joseph Casartellij Manchester. 



This anemometer consists of a fan, or plate, made of light material, sus- 

 pended in a frame on delicate centres, having a balance weight attached to 

 the top of the fan. To one side of the frame is fixed on pivots a quadrant 

 opening out at right angles to the fan, and on it is marked the velocity cf 

 the current in feet per minute, as indicated by the angular rise of the fan upon 

 which the current impinges. The advantage of the instrument consists in 

 the fact that it requires no timing as required by every other instrument, and 

 from actual experiment it is found as accurate as the most delicate instrument, 

 and very convenient. 



410h. Improved Biram's Anemometer. 



Joseph Casartelli. 



The improrement in this instrument consists in the fan being made of light 

 material, thus greatly diminishing the friction, and rendering it a delicate and 

 useful instrument. 



4:101. Biram's Patent Anemometer for ascertaining the 

 current of air in mines, air flues, &c. John Davis and Son. 



This anemometer registers up to 1,000 feet. At the bottom there is a tube 

 in which a stick may be inserted, so that the experimenter can stand at a 

 distance from the instrument, otherwise the current of air would be deflected 

 by the body of the experimenter. 



The vanes may at will be disconnected from the indices by means of a stud 

 at the side, thus rendering the process of timing more simple and exact. 



410k. Biram's Patent Anemometer for ascertaining the 

 current of air in mines, air flues, &c. John Davis and Son. 



The 4" anemometer indicates up to 10 million feet. The size and angle of 

 the vanes are calculated by mathematics and corrected by experiment, each 

 instrument being corrected separately. 



The registering apparatus consists in the 4 in. new anemometer of six small 

 circles, marked respectively X, C, M, X M, C M, and M, the divisions on 

 which denote units of the denominations of the respective circles ; in other 

 words, the X index in one revolution passes over its ten divisions and registers 

 10 x 10 or 100 ft. ; the C index in the same way 1,000 ft. ; and so on up to 

 10.000,000 ft. ; so that an observer has only to record the position of the 

 several indices at the first observation (by writing the lowest of the two figures 

 on the respective circles between which the index points in their proper order), 

 and deduct the amount from their position at their second observation, to as- 

 certain the velocity of the air which has passed during the interval ; this mul- 

 tiplied by the area in feet of the passage where the instrument is placed, will 

 show the number of cubic feet which has passed during the same period. 



The novelty in this anemometer is in its extreme portability and substantial 

 workmanship ; it is supplied with a lever which disconnects, at will, the vanes 

 from the indices, thus rendering the process of timing more simple. 



