178 



SCIENCE. 



[N. S. Vol. XVI. No. 396. 



grees from 20° to 70°. A quantity of mer- 

 cury was kept at a constant temperature, 

 while a known volume of an inert gas was 

 passed through in such a way as to become 

 saturated with the vapor of mercury. From 

 the loss of weight of the mercury, and the 

 volume of the gas when at the temperature 

 of the merciiry can be computed the weight 

 of vapor in unit volume, and the vapor- 

 pressure. 



Carbon dioxide was freed from accom- 

 panying hydrochloric acid by passing 

 through sodium acid carbonate, and dried 

 by phosphorus pentoxide. The mercury 

 was contained in a spiral absorption appa- 

 ratus. By a somewhat elaborate apparatus, 

 a hundred liters of water were kept at a 

 temperature constant within two or three 

 hundredths of a degree. In an air-bath in 

 this water were placed two absorption 

 apparatus containing mercury. In one, gas 

 passed at a rate of about thirty liters in a 

 day, while the current was a third more 

 rapid in the other. As both rates gave the 

 same final values, it was thought that in 

 both the gas had been saturated. The 

 observed loss was always made as much as 

 about ten milligrams; at the lower tem- 

 peratures this required some twenty days. 



Van der Plaats, in 1886, made determina- 

 tions at 0°, 10° and 20°. About the same 

 time the writer made determinations at 15°. 

 All the observations, whether recent or 

 older, are represented by the interpolation 

 formula 



Briggs Log P = — 4 + 0.6020 -|- 0.0-2718 T, 



which gives the pressure in millimeters of 

 mercury. The greatest difference between 

 observation and formula is 0.0008 mm. and 

 the mean difference is 0.00025 mm. The 

 extrapolation formula of Hertz agrees 

 with, observed values at 20°, but is in excess 

 by thirty per cent, at the higher tempera- 

 tures; the formula of Ramsay and Young 

 agrees with observation nearly as well. 



On the Feasibility of Tfansmiiting Terres- 

 trial Heat into Available Energy: Jacob 

 Wainwright, Chicago. 

 This paper has been published privately 



by the author. 



On the Conditions Co7itrolling the Drop of 



Potential at the Electrodes in the 



Vacuum Tube Discharge: C. A. Skinner, 



University of Nebraska. 



The paper was presented by Professor 

 Zeleny and will later be published in the 

 Philosophical Magazine. 



The drop of potential at the electrodes 

 is supposed to be due to the difficulty of 

 the carriers to give up their charges to the 

 metal on account of the velocity of impact. 



This velocity must first be reduced, 

 which is done by repeated bounding away 

 from the electrode, the coefficient of restitu- 

 tion being taken as less than one. An 

 equation was obtained for an ideal simpli- 

 fied case for the time required for the car- 

 rier to be brought to rest. The longer this 

 time, the greater is the fall at the electrode 

 on account of the aceiuiiulation of the car- 

 riers at the surface. 



Experiments in which some of the quan- 

 tities involved were varied gave results in 

 harmony with the above view of the cause 

 of the drop at the electrodes. 



On the Rotary Dispersion of Fuchsine So- 

 lutions: F. J. Bates, University of Ne- 

 braska. Read by title. 



Sparking Potentials for Small Distances: 

 E. Earhart, Rose Polytechnic Institute. 

 Read by title. 



On the Magnetic Behavior of Nickel-copper 

 and Nickel-tin Alloys: Bruce V. Hill, 

 University of Nebraska. Read by title. 



Some Observations Showing the Oscillatory 

 Character of Lightning: A. AA^. Smith, 

 University of Mississippi. Read by title. 



