

III. ANALYSIS AND SYNTHESIS. 185 



This apparatus is too well known already to require in this place a 

 more detailed description as regards its capabilities. It will therefore be 

 necessary to give only a short explanation of the reading indications on the 

 Lamellae, and to refer, as to all specialities respecting this apparatus, to 

 Prof. Melde's publications. Poggendorff's Annalen, Vol. CXIV., page 117, 

 " Lehre von den Schwingungs-Curven," by Dr. Franz Melde, p. 25. 



The great Lamella has on each side a line as a mark, and on its upper end 

 the figures I. and II. ; the smaller Lamellae have the same figures I. and II., 

 and on each side three lines. 



If the great Lamella is placed upon the mark of side I., and the small 

 Lamella on the line of side I., with the indication ^, then the vibrations of 

 both Lamellae to each other are as 1 : 4. The indications of side II. naturally 

 correspond to the mark of side II. on the great Lamella. 



The Lamella with the little mirror is used when the curves are to be shown 

 to a whole audience, for which purpose the apparatus ought to be so placed 

 that the rays of the sun, or electric light, falling on the mirror are thrown 

 either on the ceiling or on the wall of the room. 



The round bars serve for the production of oscillating curves of two ellip- 

 tical vibrations. 



Finally, it is to be observed that the apparatus may be used equally well 

 for fixing the vibration curves, for which purpose a phonautograph is em- 

 ployed, the cylinder of which is covered with a paper, as smooth as possible, 

 on which soot is lightly scattered. 



A small piece of the top of a feather fastened with wax upon one of the 

 smaller Lamellae will be sufficient to describe the curves. In this case, the 

 oscillating surfaces ought to be parallel. 



721. Atlas, belonging to the same, illustrative of the theory 

 of oscillation curves, by Dr. F. Melde. 



Ferdinand Suss, Marburg. 



722. Melde's Tuning-fork Apparatus for producing 

 stationary waves on a thread. 



(See Poggendorff's Amialen, vol. 109, p. 193 ; and vol. Ill, 

 p. 513.) Ferdinand Suss, Marburg. 



In Poggendorff's Annalen, Vol. CIX., p. 193, and Vol. CXI., p. 513, a de- 

 tailed description is given of this apparatus, and of several experiments made 

 with it ; also an account of the theory of the oscillation curves (" Lehre von 

 " den Schwingungscurven "), by Dr. Franz Melde, p. 94. 



By means of the small sliding rod of glass which is screwed into one of 

 the prongs of the fork, and rubbed with wet fingers, the tuning-fork is 

 brought into a state of vibration. (The small glass rod, owing to its fragility, 

 must be inserted reversely into the wooden frame, when not used, so that only 

 the brass neck of it is visible.) On the lower part of the tuning-fork there is a 

 peg for tuning, which takes up one end of the thread, and serves for stretching 

 it. From this point the thread passes through the neck of the other prong 

 of the fork to a clamp admitting of adjustment to any point of the bar, which 

 is about a meter in length, and thus allows of any length of the thread up to 

 this limit. In order to read the length of the thread, there is on one of the 

 narrow sides of the bar a division indicating half centimeters. 



The tuning-fork can be turned about its vertical axis in such a way that its 

 surface of oscillation falls in a parallel line with the longitudinal direction of 

 the thread, perpendicular to it, or at any other selected angle. 



The bar can be turned about a horizontal axis, and arrested in any desired 



