PHYSICS. 97 



made at pressures varying from TOO to 2200 millimeters. 

 The results obtained confirmed the conclusions of Regnault, 

 although showing numerical differences in the values ob- 

 tained, and proving, for instance, that the deviations of air 

 from Boyle's law are even less than appeared before. But 

 the most important result of the researches is that the di- 

 vergences from Boyle's law, shown by the air being negative 

 at pressures above the mean atmosphere, as was observed by 

 Regnault, proved to be positive (volume decreases slower 

 than pressure increases) at pressures below it. We must, 

 then, conclude that the air experiences a change o.'eompress- 

 ibility at a certain pressure about the mean of that of the 

 atmosphere ; and this conclusion is supported by the circum- 

 stance that such a change has been also noticed in carbon 

 dioxide and sulphurous oxide gases, but at pressures far 

 lower than is the case for air. Only for hydrogen does the 

 divergence continue positive for all pressures. Altogether 

 we must conclude that the deviations from Boyle's law are 

 far more complicated than has been suspected. 



Romilly has communicated to the French Physical So- 

 ciety the results of his experiments on the use of a jet for 

 aspirating and condensing gases. He finds, 1st, that the jet 

 should be placed at a distance from the receiving tube equal 

 to about four times the diameter of this latter tube; and 2d, 

 that the conical opening of 6 given by Venturi for water is 

 the best angle for air also. The first point is proved by find- 

 ing that a gasometer is filled in two minutes forty seconds 

 when the jet is placed in the interior of the receiving cone, 

 in eight seconds when it is withdrawn a little from this cone, 

 and in three seconds when it is removed four times the di- 

 ameter of the cone. If a cone of 8 be substituted for the 

 Venturi cone of 6 in the above experiment, sixteen seconds 

 is required ; and twenty-four seconds is necessary if only an 

 opening in the thin Avails of the vessel is used. Moreover, 

 Romilly finds that the maximum effect is not obtained when 

 the jet is central. The point of maximum effect varies with 

 the distance between the jet and cone, the locus of these 

 points constituting an ellipse. 



Frankland has presented to the Royal Society a paper on 

 the transport of solid and liquid particles in sewer gases 

 a subject of great hygienic importance in reference to the 



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