Chemistry and Physics. 591 
foldings of stratified rocks evidence of analogous vibrations. The 
ventral segments of a liquid vein, M. Barthélemy thinks, are pro- 
duced by the iss 208 ed the liquid mass upon which it falls 
reacting upon it n makes an ingenious application of these 
s to account for the Domine of stratification produced by 
electric saws in rarefied media.—Ann. Chim. Ph hye. “ A 
oS Jan., — 
5. Expa 
series of oe on the expansion of gases, and a new for orm of 
air-thermometer. His apparatus consists of a bulb tube containing 
the gas to be studied, connected by a long rubber tube, contain- 
ing mercury, with an open cylindrical manometer tube. By va ry- 
ing the height of the latter the pressure may be altered at will. 
e volume of the gas is always rendered sop the same by 
bringing the mercury just in contact wit a glass point inside the 
bulb tube. The observation therefore consists in measuring the 
pressure at various temperatures. The coefficient of expansion of 
various gases was thus determined with the following results. The 
numbers are multiplied by 10° or one million, to render a compari- 
son more convenient. e coefficient for air was found, from 
20 measurements, to be 3669" 6, while Rudberg found it 3645: is 
Regnault 3665, and Magnus 3667°8. Hydrogen sie aresult 3656°2 
nitrogen 3667° : oxygen 3674°3, carbonic acid 3706°7- The same 
instrument is also mens employed as an air- Picesialician —Pog- 
sore fe 8 hers p. 8 E. . P. 
the pressure of the gas in one Soft @ wtih or on turning the done 
ble plates, a series of dark lines are produced in the spectrum 
known as Talbot’s bands. In ase, calling D the difference in 
and /7 the pressure to which the gas is subjected, it is eras that 
We may express the value of n by the equation n—I=a , 
in which a@ and B are constants. In the same whe Rigaanis 8 re- 
Sults for pressures under 8 atmosp! show that ia (1+Bf), 
so that if the excess of refraction n—1 is Faroe to the dens- 
ity d of the gas, the two coefficients } B and B’ should be equal. : 
‘In the following t table are given for various gases the values of 
B’ as determined by Regnault and } B measured as described 
above. We may remark that the refraction and compressibility 
vary alike, in one direction for hydrogen and in the opposite way 
