October 18, 1901.] 



SCIENCE. 



593 



ature, although diminishing with time, if 

 the wire has just been hotter than if it has 

 just been colder. The conditions at the 

 surface of the body at these temperatures 

 reach their steady state but slowly, while 

 for temperatures below 100° C. this is ac- 

 quired much more rapidly. Changes in the 

 molecular arrangement of the body, as well 

 as the amount oft he occluded gas, may 

 play a large part in the phenomenon. 

 From an iron wire the rate of discharge 

 while small at the lower temperatures be- 

 came many times larger at the higher tem- 

 peratures. It was also found that a posi- 

 tively charged body does not lose any 

 charge due to the action of the light, even 

 when its temperature is raised to that of 

 red heat. To get an explanation for the 

 unipolarity of the photo-electric effect, we 

 need but consider that the intra-molecular 

 impulses which are produced by the light, 

 and which give rise to the discharge, are 

 able to throw off from the body the nega- 

 tive ions or corpuscles, but are not able to 

 disengage the much larger positive ions for 

 which the forces of restitution are corre- 

 spondingly greater. 



14. * The Diminution of the Potential 

 Difference between the Electrodes of a 

 Vacuum Tube produced by a Magnetic 

 Field ' : John E. Almy. 



15. ' Note on the Discharge Current from 

 a Surface of Large Curvature ' : John E. 

 Almy, University of Nebraska. 



The discharge from a wire to a surround- 

 ing concentric cylinder, with reference to 

 discharge current, especially, is studied. 

 The law of discharge, under the conditions 

 given below is found, I = aV {V — b)L/R^, 

 where 



/=the discharge current, passing from wire to 

 cylinder. 



V^ the potential difference between wire and cyl- 

 inder. 



L = the length of the wire. 



B = the radius of the cylinder. 



6 = a constant, with given apparatus and gas 

 pressure, and is very approximately the ' minimum 

 potential ' of Eontgen. 



a = a constant. 



The applicability to the discharge was 

 shown with gas pressures, from 20 to 75 cm. 

 of mercury, with cylinders, up to 10 cm. in 

 diameter. The proportionality of current 

 to wire length holds so long as the wire 

 length is greater than the radius of the cyl- 

 inder used. Finally, the proportionality 

 of current to the inverse cube of the cylin- 

 der radius does not hold accurately. More 



strictly speaking it may be said that I cc — 



and 3.3 > 71 > 2.8, in the experiments 

 made. 



16. ' The Radiant Efficiency of Vacuum 

 Tubes ' : E. E. Roberts. 



17. ' On the Spark Discharge during 

 Rapid Oscillations': K. E. Guthe. (By 

 title.) 



18. ' Results of Recent Magnetic Work 

 of the U. S. Coast and Geodetic Survey ' : 

 L. A. Bauer. (By title.) 



19. ' The Physical Decomposition of the 

 Earth's Permanent Magnetic Field ' : L. A. 

 Bauer. (By title.) 



20. ' On the Calorimetric Properties of 

 the Ferro magnetic Substances, with special 

 reference to Nickel-steel ': B. V. Hill. 



It is well known that the ferro-magnetic 

 substances when heated through a certain 

 range of temperature, depending on the na- 

 ture of the substance, absorb latent heat 

 and pass into an allotropic modification in 

 which they are non-magnetic. Certain al- 

 loys (e. g., nickel-steel) having been trans- 

 formed into this state by heating, maintain 

 it down to comparatively low temperatures, 

 so that there are many so-called irreversible 

 nickel-steel alloys to be obtained in both 

 modifications within the same range of tem- 

 perature (20° to 300° C). This allows the 

 properties of the alloys in the two states to 

 be compared. 



