198 



by the size and t'ne tlii;-lviiess of the membrane, which is quite 

 a natural thing, considering that the membrane vibrates all over 

 ("en masse") with the greatest excnrsion in the centre. The tech- 

 niqne damps it to a certain extent in varions degrees of efficiency 

 (damping cansed by air and l^y induction). In circuit with this 

 telephone is the microplione varying considerably as to the number 

 and the size of the carbon grannies. Without exception 1 used for 

 the microphones coal-membranes tuning with the telephone dia- 

 phragm selected beforehand, and I regulated the damping by select- 

 ing grannies of a particular size. This can easily be managed, so 

 that harmony for a broad zone may readih' be effected, which is 

 requisite for a proper reinforcement and audibility to be guaranteed 

 by the circuit. 



The graphic representations show, that much can be attained in 

 the indicated way even with the present means. If the technique 

 could be improved so as to enable us to apply the principles here 

 brought forward, I doubt not but telephony in private houses, in 

 churches and in assembly-rooms would be made subservient to a 

 much greater number of pathological organs of hearing than the 

 attainable means allow, seeing that hitherlo only reinforcement was 

 the object of experimenters and thai a reinforcement not always in 

 a zone of sufficient breadth. A new field of research opens up when 

 the zones of reinforcement are extended to different portions of the 

 speechzone a^ to e^. Every ear will then be able to select an 

 apparatus complemental to what it lacks. 



Chemistry. — "On the synthesis of amido-oxalylhiuret 



CO NH, 



CONHCONHCONH,". 

 By Dr. J. Th. Bornwatkr. (Communicated by Prof. 

 A. P. N. Franchimont). 



(Communicated in the meeting of June 28, 1913). 



In 1911, I showed that oxalyldiureid is not identical with 

 the compound obtained by Grimaux (Bull. 32 (1879) p. 120) on 

 heating parabanic acid with urea and which in the German literature 

 is called wrongly oxalyldiureid, although Grimaux rightly calls it 

 "amide d'un acide oxalylbiurétique". 



