﻿new Harmonic Analyser. 119 



number of readings at once. The new instrument is there- 

 fore constructed to record up to 200 centim. 



§ 7. Last summer at the Munich Exhibition Herr Coradi 

 submitted a new arrangement to me to obviate some of the 

 imperfections of the instrument described, and this he has 

 since carried out with an ingenuity which 1 cannot enough 

 admire. He has practically got rid of all the imperfections of 

 the old Analyser, and has now produced an instrument which, I 

 fancy, leaves nothing to be desired. He himself says it is 

 the best instrument of any kind he has yet made. The 

 chief alteration is this, that he interposes between the register- 

 ing-wheel at the lower end of the spindle and the cylinder a 

 perfectly free glass sphere. 



Fig. 4. 



The " spindle " has now firmly attached to its lower end a 

 square frame K L M 1ST (comp. figs. 3 and 4) by aid of two 

 solid rods K and M, instead of carrying the ring connected 

 by aid of an elastic spring. This frame holds two registering- 

 wheels R 1 and R 2 , whose axes K L and L M are at right 

 angles. Between these lies the glass sphere Gr,. resting with 

 its lowest point on the cylinder belonging to the spindle. A 

 third wheel r at N is by aid of a spring pressed against the 

 sphere to secure contact between the latter and the registering- 

 wheels. If, now, the tracer follows the curve this frame will 

 turn with the spindle, the three wheels will carry the sphere 

 with it, which will turn pivot-like on its lowest point. If, as 

 in fig. 4, the plane of one wheel R 1 makes with the axis of x 

 an angle n0, and if in this position the tracer, and with it the 

 whole instrument, is moved through the distance dy, the 

 " shaft " will turn proportionally to dy. This will set the 

 sphere turning about its horizontal diameter xx parallel to the 



