468 SCIENTIFIC RECORD FOR 1882. 



the cylinder is inverted and the sohd piston is covered at top with 

 mercury, thus avoiding all waste space. At each stroke it comi)resse8 

 one-third of a liter of gas, and its capacity is such that a condensation 

 to two hundred atmospheres may be attained. Lubrication is effected 

 by vaseline. {Comptes Rendus, March, xciv, p. 626; J. P%s., October, 

 II, I, p. 449.) 



Amagat has j)lotted the curves of the compressibility of nitrogen, 

 obtained in his experiments and in those of Cailletet, with pressures 

 as abscissas and the products pv as ordinates. That of Amagat is a 

 smooth curve, while that of Cailletet has a deep point of inflection at 

 a pressure of sixty meters of mercury. Amagat criticises the appara- 

 tus of Cailletet as inaccurate. {Comptes Rendus, October, xcv, p. 638.) 



Hautefeuille and Chappuis have liquefied ozone by subjectiug it, 

 mixed with oxygen, in a Cailletet pump, to a pressure of 125 atmos- 

 pheres, the tube being recurved and immersed in a jet of liquid ethy- 

 lene, which cooled it probably below — 100° C. The ozone was ob- 

 tained in liquid drops of a dark indigo blue color, which may be 

 preserved for some time even under atmospheric pressure. {J. Phys., 

 November, II, i, p. 493.) 



Neyreneuf has extended the formula of Bernouilli for the flow of 

 gases through orifices in thin plates to the case where the flow is 

 simultaneous through two orifices at different levels. He has obtained 

 a very sensitive gas level in this way, a new sort of chemical barmou- 

 icon, as well as new sensitive flames. [Ann. Chim. Phys., February, Y, 

 XXV, p. 167.) 



Ville has devised a gas regulator which is independent of the press- 

 ure. It consists of a U tube containing mercury, communicating on 

 one side with the space where the pressure is to be kept constant, and 

 on the other with the reservoir where the gas is compressed. If the 

 pressure falls in the former, the mercury rises in the tube and makes 

 electrical contact by means of a nickeled-steel wire, thus sending a cur- 

 rent through an electro- magnet which controls a valve, thus lifting the 

 valve and allowing gas to pass from the reservoir into the other vessel. 

 Then the column of mercury falls, the contact is broken, and the valve 

 closes. The apparatus used by the author will withstand a pressure of 

 15 atmospheres and controls the pressure within one-quarter of a mil- 

 limeter of mercury. {Comptes Rendus, March, xciv, p. 724; J. Phys., 

 July, II, I, p. 327.) 



Berthelot and Yieille have determined the velocity of gaseous explo- 

 sion through tubes. They find as a mean that in a mixture of elec- 

 trolytic oxygen and hydrogen this velocity is 2,810 meters, and in a 

 mixture of carbonous oxide and oxygen 1,089 meters per second. Curva- 

 ture of the tube did not change the value, nor did alteration ot the 

 material of which it was made. The velocity was the same whether the 

 tube was open or closed, is uniform throughout its length, and is inde- 



