III. ANALYSIS AND SYNTHESIS. 157 



The other part consists also of- a Lamella, which is brought into vibrating 

 motion by an electro-magnet, and the vibration surface of which can be 

 placed at any desired angle to that of the first Lamella. 



In order to put the apparatus in motion for experiments both parts must be 

 firmly fastened with vice pins, either to a long, or on two separate solid tables, at 

 such a distance (about 8-12 feet) from each other that the thread when strained 

 measures 3 to 3'5 meters in length. (The thread can, of course, be shortened 

 at pleasure, as well as be replaced by one a few meters longer ; but for college 

 experiments the length stated appeared to be most practical.) The thread is 

 fastened to Lamella I., and passed through the hole in Lamella II. towards the 

 swivel by which the correct tension is effected. 



The white points on the (red) thread serve for facilitating the better obser- 

 vation of the curves, and, in order to render them more prominent, the black 

 screen is placed behind the oscillating thread. The screen has on one side 

 small holes, which are hinged in the hooks of the frame of Lamella I. ; when 

 the screen is expanded, the foot of it is screwed firmly by a vice-pin to the 

 opposite table. 



Two (large-sized) chrome elements, the strength of which may be easily 

 regulated, will be best to do service as electro-motors. In the present case 

 two chrome elements were employed, each with two carbon plates, and a 

 zinc plate, of 18 cm. in height, and 6 cm. in width, joined together one behind 

 the other. 



When newly charged, it was only necessary to dip the zinc plate from 1 to 

 1 5 cm. into the acid, in order to obtain the required force of the electric 

 current. Both elements and the wire spirals of both magnets are, of course, 

 united to form one current circle. As already observed, Lamella I. serves at 

 the same time as interference, for which purpose an attachment screw is fixed 

 at the reverse end of the same, which is intended to take up the conduct wire 

 leading to the battery. In the attachment screw, which is in connexion with 

 the mercury bowl, a wire is fastened, which is to be connected with the first 

 attachment screw of the wire spirals, if the numbers of the vibrations of the 

 two Lamellae are to be in proportion as 1:1 a 1:2 (accord, octave). If 

 Lamella II. is to perform three or four vibrations in the same time in which 

 Lamella I. makes only one vibration, then only one wire spindle of Lamella I. 

 is set in motion by fastening the wire coming from the mercury bowl in the 

 centre attachment screw. The current must always be so powerful that the 

 interference, whose rough displacement is effected by raising and lowering the 

 platinum pin, and the more minute displacement by turning the mercury bowl, 

 can be so placed, that the shutting off of the current is effected as quickly as 

 possible, as hereupon the purity of the figures chiefly depends. 



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

 lowering the electro-magnet, which is kept in its position by the nut of a 

 winged screw, and on Lamella II. by screwing in and out the iron coves, 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 coves 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. 



I a I 

 the latter is moved to the back, marked with the annotation ; ^- 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 

 1 a 1 

 T tlle oscillations of both Lamellae are as >:3 (S fifth of the octave) 



