192 ANNUAL OF SCIENTIFIC DISCOVERY. 



he observer. 3. The time the sound takes to travel 100 (or 

 1,000) times the measured distance of the origin of the sound, from 

 the observer. 4. The time the sound takes to travel 100 times (or 

 1,000 times, as the case may be), the measured distance. Now, the 

 first, second, and fourth of these portions of time can be readily 

 eliminated by repeating the same series of observations exactly (the 

 clock being wound up at the commencement of each series exactly to 

 the same extent) ; the observer, on the second occasion, placing him- 

 self at one-half, or one-fourth, or at any determined part of his pre- 

 vious distance from the origin of sound ; or by placing himself close 

 up to it, using the same wires for the galvanic circuit on each occa- 

 sion, in order to eliminate the fourth portion. The author was not 

 fully aware of the exact mechanism by which Prof. Piazzi Smythc dis- 

 charges the cannon which he has introduced as time-signals, but he 

 had no doubt it could be adapted to this method, and thus determine 

 experimentally whether the velocity of sound is affected by the vio- 

 lence of its originating cause : a question which Mr. Earnshaw has 

 from theory decided in the affirmative. It would, however, involve, 

 the author supposed, the use of two cannon, each alternately to be 

 in process of being charged while the other was at work. This, how- 

 ever, could be readily accomplished. 



UNEQUAL POWER OF THE ORGANS OF HEARING. 



In making experiments with tuning-forks by holding one to each 

 ear at the same time, HerrFessel, of Cologne, has discovered the ears 

 do not possess an equal power of hearing. It appears that from nu- 

 merous trials on various individuals the hearing is generally best 

 with the right ear. A similar difference in the power of the right 

 and left eye is also more common than is generally supposed, as the 

 impression made on the weaker eye is absorbed or dissipated by the 

 stronger. 



NEW ANEMOMETER. 



The object of a new anemometer, described at the last meeting of 

 the British Association bv Mr. C. Cator, was to obtain bv the wind 



/ * 



acting on one surface only, a daily curve of its pressure in pounds on 

 an area of a square foot, and the number of miles traveled by it in a 

 horizontal direction in 24 hours, or any other given time, and 

 thence its hourly velocity. The surface upon which the wind acts, 

 or the pressure-plate, is the base of a cone, the axis of which is hori- 

 zontal, and the area of the base equal to one square foot, the object 

 of the cone being that there shall be as little resistance as possible, 

 and to neutralize the effect of a vacuum being formed behind it. 

 The pressure-plate is attached to the end of a horizontal bar, and with 

 it is moved backwards and forwards, the bar resting on friction-roll- 

 ers. This is the only portion of the instrument out-of-doors and ex- 

 posed to the weather. A chain attached to the horizontal bar passes 

 down through a tube as a connection with the rest of the instrument 

 within the building on which the anemometer is fixed. The pressure 

 of the wind is measured by two curved levers of equal length acting 

 against each other, their motion being in a vertical plane. At one 

 end of the upper lever is a fixed weight, and to the opposite end of 



