Intelligence and Miscellaneous Articles. 309 



unsettles the general representation of the values. So that in 

 every case, without exception, the general representation of 

 the behaviour of rings, furnished by calculation on the basis 

 of a fixed saturation limit, has been far better than any ob- 

 tained by using a variable saturation limit. At the same 

 time it must be admitted that experiment sometimes shows a 

 heightening of the apparent saturation limit as it is approached . 

 The change, however, resembles rather a change in the pro- 

 perties of the metal than a continuation according to the same 

 laws which successfully represent the general course of the 

 values. 



I must reserve for another occasion some considerations as 

 to dynamo machines, founded on the numbers here obtained 

 for bars with pole pieces. 



It must be noticed that the bars here dealt with are only of 

 one definite shape, viz. diameter : length : : 1 : 20 or there- 

 abouts. And the object of the investigation was to get a 

 series of reliable data with respect to this one shape, which 

 might afford a sound starting-point for the investigation of 

 other proportions. 



XXXVI. Intelligence and Miscellaneous Articles. 



MEASUREMENT OF PITCH BY MANOMETRIC FLAMES. 

 BY M. DOUMER. 

 TVTANOMETRIC flames have hitherto only been used as a 

 ■^-*- means of demonstration, and for studying the quality of 

 vowel sounds. They are, however, susceptible of more varied 

 applications, and may in particular vie with the graphical method 

 in studying the height of sounds. 



For this purpose two adjacent manometric flames are taken, one 

 of which is due to a sound of known height, the other to a 

 sound the height of which is to be determined, and then by means 

 of a rotating mirror it is ascertained how many vibrations of the 

 sound under investigation correspond to a known number of vi- 

 brations of the chronograph. A simple proportion gives the desired 

 height. 



This method, which is very simple in theory, is in practice com- 

 plicated, and almost impossible from the want of centering of the 

 mirror. But it retains all its simplicity, and a certain elegance 

 moreover, if we substitute a sensitive plate for the rotating mirror ; 

 in other words, if the tw r o manometric flames are simultaneously 

 photographed on the same plate. 



The camera obscura used is a broad one, provided with a lens of 



