512 Scientific Intelligence. 



noticed. The layers occasionally had an abrupt lateral ter- 

 mination, like the edge of a volume of thick fluid poured upon 

 a flat surface. 



Besides the layer formation, turquois was also noticed in 

 small dots and in isolated patches, which occasionally differed 

 from the vein matter in being of a more bluish shade. The 

 prevailing color, however, was the green, common to the 

 American turquois, and typified at Los Cerillos. 



Turquois is known to occur at two other points in Grant 

 County, New Mexico, both of them in the Burro Mountain 

 district. From one of these the writer has specimens, con- 

 sisting of sheets of very thin turquois having several square 

 inches of surface area and from which gangue matter similar 

 to that at the locality near the copper mine has been entirely 

 removed by decomposition. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On the Compressibility of Hydrogen, Oxygen and Nitrogen. 

 — Amagat has subjected hydrogen, oxygen, nitrogen and air to 

 pressures varying from one hundred to one thousand atmo- 

 spheres, at temperatures of 0°, 100° and 200°. He finds that for 

 hydrogen the values of dv/dt are practically independent of the 

 temperature, the coefficient of expansion diminishing regularly 

 as the pressure increases ; while for nitrogen, oxygen and air, 

 this coefficient passes through a maximum corresponding to the 

 pressure at which the product pv has its minimum value. The 

 values of dp'dt for hydrogen are also practically independent of 

 the temperature, and nitrogen and air resemble hydrogen in this 

 respect. Indeed the properties of hydrogen seem to be limiting 

 values toward which those of all other gases tend ; these limiting 

 values of dv/dt and dp'dt being independent of the temperature, 

 the former diminishing and the latter increasing as the pressure 

 rises, the change being regular in both cases. At pressures up to 

 3000 atmospheres and at all temperatures, the isothermal lines 

 have been shown by later experiments not to be exactly straight 

 lines but to have a slight concavity toward the axis of abscissas. 

 — C. R., cxi, 871 ; J. Cheni. Soc, lx, 378, April, 1891. G. r. b. 



2. On Osmotic Pressure. — In 1888, an analogy was pointed out 

 by van't Hoff between the physical condition of a substance in 

 dilute solutions and in the gaseous condition, osmotic pressure in 

 the former case being the analogue of vapor-pressure in the 

 latter. Boltzmann has now investigated osmotic pressure mathe- 

 matically from the standpoint of the kinetic theory of gases. He 

 supposes a cylinder, having a semi-permeable septum in the 

 middle dividing it into two equal parts, and having its ends 



