

III. ANALYSIS AND SYNTHESIS. 187 



The intensity of the vibrations on Lamella I. is regulated by raising and 

 lowering the electro-magnet, which is kept in its position by a set screw, 

 and on Lamella II. by screwing in and out the iron cores, and by the shifting 

 the whole magnet. 



With a powerful current the vibrations will be most regular when the 

 magnet is entirely moved back, and the cores are screwed so closely to the 

 Lamella that the contact just ceases. 



Lamella I. has only one mark on which it always remains accurately 

 adjusted. If it is required that it should oscillate uniformly with Lamella II. 



1 a 1 

 the latter is moved to the back, marked with the annotation j and upon 



the spot marked with x the weight is placed with the annotation i. If the 

 weight is removed further from Lamella II. the oscillations of the two La- 

 mellae are as 1:2. If Lamella II. is moved to the mark indicated by 

 I a I 

 2 the oscillations of both Lamella are as 1:3 (S fifth of the octave). 



By placing the weight with the annotation ^ upon the spct indicated with x 

 on Lamella I. the oscillations are as 1 : 4 (double octaves). 



The two smaller weights of different size serve for the more exact regula- 

 tion in case great changes in the temperature, or simultaneous oscillation of 

 either one or the other of the tables, should be of injurious influence. 



Lamella II., as has been observed at the commencement, can be turned 

 about an horizontal axis, so that its vibrations can be adjusted either rectanr 

 gularly, parallel, or in any angle whatever to Lamella I. In case it is neces- 

 sary to ease and screw fast the hexagonal nut, the key is added for the purpose. 

 The small key is for unscrewing and fastening the screws which fix the 

 Lamella. 



724. Melde's Wave Apparatus, for showing the produc- 

 tion of Ghladni's figures of sound, according to the theory of 

 Wheatstone. 



(See Poggendorff's "Annalen, Jubelband, p. 101, and the 

 accompanying description.) Ferdinand Suss, Marburg. 



This apparatus has been more particularly described by Professor Melde, in 

 Poggendorff's Armalen, Jubelband, page 101. 



The present apparatus is distinguished by several differences from that de- 

 scribed in the above-mentioned work, by which the manipulation is consider- 

 ably facilitated, but before entering into this, it must be mentioned that in the 

 construction of this apparatus it was kept in view that two systems of waves 

 of equal length and equa intensity pass swiftly through a square plate. 



The upper system of waves is formed of 33 rows of 17 pins each, which 

 together make two wave lengths. The saddle upon which the pins are 

 placed corresponds to a length of 1 5 of wave lengths ; it has on two sides 

 (above and below) wave-systems, which in so far differ from one another, as 

 the one is like a system of two mountains with one valley in the middle, and 

 the other like two valleys intersected by a mountain. On the longitudinal 

 sides of this saddle rectangular zinc plates have been screwed, which are pro- 

 vided with divisions for adjusting the desired phases. 



O denotes the centre position (middle between mountain and valley). The 

 lines marked on the black board correspond to the waves formed by the pins. 

 The longitudinal line serves as index upon which the lines of the saddle are 

 indicated. 



When the saddle has been adjusted in the desired position, the board is 

 lifted by the handles fastened on the sides as far as possible perpendicularly 



