100 SEC. 3. MEASUREMENT. 



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 from theory 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. 



414. Edelmann's Anemometer with galvanic register. 



M. Tli. Edelmann, Munich. 



416. Anemometer for determining the velocity of the air, 

 and other gaseous currents in pipes and air passages. 



Moritz Gerstenhofer, Freiberg. 



C. CHRONOGRAPHS. 



4O1. Apparatus for measuring the velocity of projectiles, 

 and capable of recording several measurements on one and the 

 same trajectory and of the same projectile. 



Antoine Joseph Gerard, Liege. 



403. Ballistic Chronoscope, with t\vo pendulums, for ascer- 

 taining the speed of a projectile at any point of its trajectory, by 

 measuring the time of flight of a portion of the trajectory ; also 

 for measuring portions of time between one tenth of a second and 

 25 seconds. Lieutenant- General Leurs, Brussels. 



404. Electric Chronograph, for measuring the initial velo- 

 city of projectiles. Le Boulenge, Liege. 



405. Electric Clepsydra, for measuring the time of flight 

 of projectiles. Le Bouletige, Liege. 



405a. Electro-Ballistic Apparatus, for determining the 

 velocity of a projectile, with description of experiments and addi- 

 tional apparatus. M. Navez, Paris. 



406. Electric Chronograph for the measurement of minute 

 portions of time, &c., &c. Lieut. H. Watkin, R.A. 



This instrument consists of two upright cylinders resting on a base of wood ; 

 between them, suspended by an electro-magnet, is a weight with projecting 

 arms. The cylinders being connected with the secondary circuit of'an indue- 



