476 Intelligence and Miscellaneous Articles. 



are all given, the table containing in all a record of about 4600 

 lines, extending from the region of the lithium (red) line to the 

 extreme ultra-violet. After this follows a table of the air-lines of 

 the solar spectrum, with their relative intensities when the sun is 

 on the horizon and at medium altitude. The measurements from 

 which this table was compiled are those of Becker, and the lines 

 number about 1000. The volume is completed by a list of 14 

 lines in the spectrum of gadolinium chloride, the work of Lecoq 

 de Boisbaudran, and 74 lines in the spectrum of a vacuum tube 

 containing hydrogen, measured by Ames of the Johns Hopkins 

 University. The latter measurements are rendered more interest- 

 ing by their being compared with the values obtained from. Balmer's 

 formula, in which the oscillation frequency is taken as 2741 8*3 

 (1 — 4/m 2 ), different values of m giving different lines. The agree- 

 ment between the theoretical and actual frequencies is in many 

 cases very remarkable. Jaxces L. Howabd. 



LY. Intelligence and Miscellaneous Articles. 



ON THE INFLUENCE OF PRESSURE ON THE VISCOSITY OF LIQUIDS* 



BY R. COHEN. 

 rPHE results of a long experimental investigation on this subject 

 -*- are stated by the author as follows : — 



I. The viscosity of water is diminished by pressure up to tem- 

 peratures of 40°, as had already been found by Kontgen, Warburg, 

 and Sachs. 



II. No minimum of viscosity can be observed up to pressures of 

 900 atmospheres, and temperatures of 25°; the change of viscosity 

 is not proportional to the pressure, but increases more slowly. 



III. In the case of water the viscosity changes greatly with the 

 temperature, and in the interval of temperature from to 23° it is 

 greatest near 0°. It has not been decided whether the viscosity of 

 water increases with pressure for temperatures above 40°. 



IY. "With concentrated aqueous solutions of NaCl and of NH 4 C1 

 the viscosity of the solution increases with the pressure, and the 

 percentage change is almost proportional to the pressure. The 

 influence of temperature is small. 



V. The more dilute a solution of NaCl is the more does the 

 influence of the anomalous deportment of water preponderate, both 

 as regards the influence of temperature, and also the influence of a 

 further increase of pressure. From a 5-per-cent. to a 10-per-cent. 

 solution there is for each concentration a definite temperature 

 between 2° and 22 0, d, at which the influence of a pressure of 600 

 atmospheres on the viscosity is zero. 



YI. In oil of turpentine the change of viscosity with the pres- 

 sure is twenty times as great as with a saturated solution of Nad, 

 and is nearly proportional to the pressure. The direction of the 

 change is the same. The influence of temperature is small, and is 

 in the opposite direction to that of a solution of NaCl. — Wiede- 

 mann's Annalen, No. 4, 1892. 



