306 Intelligence and Miscellaneous Articles. 



ON A VIBRATORY MOTION AT THE ORIGIN OF A JET OF VAPOUR. 

 BY M. TH. VAUTIER. 



In the course of some researches which I have commenced upon 

 the flow of gases and vapours, I have observed a singular pheno- 

 menon, which was first signalized in 1826, by an engineer of Fou- 

 chambault's iron- works : — When a jet of gas or vapour flows, under 

 pressure, through an orifice, if a plate be placed normal to the axis 

 of the jet, at a certain height, it is repelled ; but when the plate is 

 lowered parallel to itself, it is attracted, and spontaneously sup- 

 ports itself at about 0-2 millim. from the orifice, oscillating about a 

 position of equilibrium and emitting a sound. 



I have succeeded, by means of a very simple arrangement, on 

 fixing some plates in that situation, in making them give forth 

 sounds high, intense, as prolonged as I pleased, and directly register 

 those vibrations. I have obtained in the tracings, undulations of 

 remarkable regularity and amplitude. 



I have directly registered the vibrations, thus kept up by a jet of 

 vapour, of a plate giving a note close to the fa# a =7250 single vibra- 

 tions per second. An electrodiapason simultaneously registered its 

 vibrations. Pressure in the boiler, 4*5 atm. ; diameter of the orifice, 

 2-7 millim. Diameter of the plate, 6 millim.; thickness, 1*5 j dis- 

 tance from the orifice, 0-2 ; amplitude of the vibrations, 0"7. Thus, 

 then, we have a chronograph directly registering j^q of a second. 



The sound which I get is intenser than that of the diapasons 

 which give the same note, and of which it has not, up to the pre- 

 sent, been possible to sustain the motion electrically in a practical 

 manner, and, consequently, to register it continuously. The appa- 

 ratus which I have prepared traces, as long as 1 please, in sharp 

 outline, regular vibrations of sufficient amplitude to be subdivided 

 in the usual manner. This subdivision is facilitated by the fineness 

 of the tracing, which is obtained by means of very sharp styles, 

 which, pressed lightly upon sheets of mica either smoked or not, 

 leave a thin stroke engraved upon those surfaces. 



Hitherto, at least to my knowledge, it has been found possible 

 at most to register, directly and continuously, the thousandth part 

 of a second, which is afterwards divided. The apparatus which I 

 use registers directly the seven-thousandth of a second ; and the 

 tracing, very thin, favours the usual divisions. The results obtained 

 by me quite recently permit me to expect to register sounds of still 

 higher pitch. I purpose to apply this chronograph to the measure- 

 ment of some rapid phenomena. — Oomptes Rendus de V Academic des 

 Sciences, March 6, 1882, t. xciv. p. 642. 



ON THE COMPRESSIBILITY OF GASES. BY M. E. SARRAU. 



1. In a memoir on the compressibility and expansion of carbo- 

 nic acid, very important when regarded from the thermodvnamic 

 point of view, M. Clausius has proposed for this gas the following 

 relation between the pressure (}■>), the volume (v), and the absolute 

 temperature (T): — 



P v-a TO + /3) (1) 



