60 On the Interference of the Aerial JVaves, ^c. 



given instant, is yet able, in a short time, to pour forth such an abundant 

 supply ; the difference between a galvanic and common electrical machine 

 being, that in the latter, though the intensity be greatly higher, yet the 

 velocity of the current is incoramensurably more slow. 



Mr. F., in his views of the passage of the opposite ions to the ex- 

 tremities where they are developed, appears to agree with those before 

 enounced by Grotthus, Biot, and others, namely, that they travel by a 

 series of successive decompositions and recompositions, the anions to the 

 anode, and the cations to the catode. 



ON THE INTERFERENCE OF THE AERIAL AVAVES PROPA- 

 GATED BY A TUNING FORK, &c. 



BY ROBERT ADDAMS, LECTtTKER ON CHEMISTRY AND NATURAL PHILOSOPHY. 



A KNOWLEDGE of thc prccisc manner in which the interference of 

 undulte takes place, is of considerable importance in the investigation of 

 the physical sciences, especially those of Acoustics and Optics. It is 

 presumed, therefore, that every new case of interference has some value as 

 confirmatory of that which is already known, or as contributing to elucidate 

 the phaenomena which are still doubtful or unexplained. With this ex- 

 pectation, I send for insertion in the West of England Journal, the 

 following account of some facts which I have obtained in reference to the 

 vibration of a tuning fork, conjointly with a resonant column of air. 



1. When a vibrating fork is held over the mouth of a pipe, whose di- 

 mensions and form are such that the included air is unisonant with the 

 fork, the sound of the latter is reinforced by the air of the former, (as first 

 demonstrated by Professor Whejitstone.) Having lately been occupied in 

 a series of experiments on the interferences of sounds, I have noticed some 

 additional evidence. Thus, let an unisonant pipe be placed vertically, and 

 a tuning fork held about half an inch from its orifice, and so that the 

 plane which passes through both its limbs parallel to their length, be 

 vertical, and consequently at right angles to the mouth of the pipe j then, 

 by moving the fork parallel to itself, the sound will be very unequally 

 reciprocated, according to the position of the fork, with respect to the 

 pipe's mouth. 



The intensity of the sound is at a maximum when the fork is over the 

 centre of the mouth ; it declines by an advance to the circumference, and is 

 at a minimum, and inaudible, when the plane of the fork is coincident with 

 a tangent to the edge or circle ; the sound begins again and increases as 

 the fork is transferred outside and beyond the pipe, where, at a certain 

 distance, it reaches its maximum, for this position, and again diminishes. 

 The same changes occur when the plane is held horizontally. 



2. If, however, the before-iueutioned plane be inclined to the axis or 



