4fS4 Miscellaneous Intellis;ence 



to' 



were, below the point of congelation. This is a circumstance shewn 

 to exist, with reg:ard to the alloy of Rose, and which might per- 

 haps be met with in many other bodies, if the changes in their 

 volume occurring near the point of congelation were examined. — 

 Annales de Chimie, xxxviii. 287. 



4. Chladni on the Propagation of Sound. — MM. Chladni and 

 Soemmering, whilst experimenting on the polarization of sound, as 

 observed and described by Weber, have remarked certain effects 

 wliich they think throw great light upon the subject, and upon the 

 propagation of sound in air. Applying the theory of liquid undula- 

 tions to those which occur in the air, M. Chladni made sonorous rods 

 vibrate in water, on the surface of which he had spread a very thin 

 layer of lycopodium for the purpose of rendering the undulations 

 visible. When a sonorous metal or glass rod is passed through a 

 liquid surface, four currents are observed about it, of which two are 

 in the direction of the vibrations of the rod, and the other two per- 

 pendicular to this direction. The currents in the direction of the 

 vibrations are outward or excentric, the two other currents are 

 entering or concentric. In all the outward currents, the lateral 

 parts are curved outwards and then converge with the entering 

 currents, so that there is found between each excentric and con- 

 centric current a circular movement representing an oval, the most 

 acute end of which is turned inwards. When a part of the excentric 

 current is thus in contact with the opposed current, it becomes 

 diverging close to the sounding rod, then reunites again with the 

 excentric current, and so on in succession : from this it results that 

 the centre of the oval seen between two currents is near to the 

 sonorous body, and that it revolves round itself. 



The excentric currents are generally longer and narrower than 

 the concentric currents. When a tuning fork is used, or any other 

 instrument with a double vibrating stem, each stem indicates its 

 own particular set of appearances. M. Chladni says, " that as 

 that which passes in aerial undulations may be understood from 

 these appearances, it becomes easy to explain the interruption to 

 the progress of sound in certain directions where the waves 

 take transversal courses," i. e. where they pass from a centri- 

 fugal to a centripetal state. — Kastner^s Archives^ vii. 233. — Bull. 

 Univ. A. X. 136. 



5. Experimental Velocity of Sound. — Experiments were made 

 on this point in Acoustical Philosophy, by MM. Myrbach and 

 Stampfer, between Untersberg and Moenchstein near Saltzbourg, 

 from August 15, to September 30, 1822. The distance was 30,601 

 French feet. The difference of level 4198 feet. The mean of 88 

 observations gave 1025.9 feet as the velocity of sound per second, 

 at the temperature of 32° F. 



6. Syphon Hydrometer, — ^A description of Mr. Meikle*s syphon 



