Chemistry and Physics. 459 



region in the ultra violet is shown to be traversed by both dark 

 and bright lines and bands. 



Jefferson Physical Laboratory, Harvard University. 



9. A New Holtz Machine. — The iniiiience electrical machine in 

 many respects has been found to excel the induction coil for the 

 excitation of X-ray tubes. H. Wommelsdoef describes a new 

 electrical machine which he calls the condenser machine. It con- 

 sists of many discs similar to those now used in the Holtz 

 machine. There is a large condenser action between the glass 

 plates which are provided with suitable sectors. We have thus 

 a row of condensers; one set of plates or coated layer remaining 

 fixed while the intervening plates revolve. 



A small model, 30^"^ high, 28='" long and with a breadth of 22=°^, 

 affords a larger quantity of electricity than the largest Holtz 

 machine, and this new machine promises to be of the greatest use 

 in the excitation of X-ray tubes. — Ann. der Physik, No. 11, 1902, 

 pp. 651-659. " J. T. 



10. Electrical Conductihility of Metals and their Vapors. — 

 Hon. E,. J. Steutt finds that (1) Mercury vapor is an insulator, 

 while liquid mercury is a conductor. Since the liquid and satu- 

 rated vapor are indistinguishable above the critical temperature, 

 one or both of these must undergo a remarkable change of elec- 

 trical properties as that temperature is approached. 



(2) Attempts to predict the critical temperature of mercury 

 seem to lead to results altogether inconsistent with one another. 



(3) Attempts to observe the critical temperature of mercury 

 and arsenic in quartz tubes have failed. In both cases experi- 

 ment proves that the critical temperature lies above a dull yellow 

 heat. 



(4) Up to a full red heat the conductivity of saturated mer- 

 cury vapor remains of quite a different order of magnitude from 

 that of the liquid, the latter being ten million (10^) limes as great 

 as the former. But on the other hand, tbe conductivity of the 

 saturated vapor is immensely greater than that of the vapor at 

 atmospheric pressure. For the former was found to have a 

 resistance of 10^ times that of the liquid, the latter more than 

 4x10^* that of the liquid. Thus the vapor at atmospheric pres- 

 sure has a resistance about 4X10^ times that of the saturated 

 vapor, both at a full red heat. It need scarcely be said that this 

 ratio is of quite a different order from the ratio of the densities 

 of those vapors. It seems likely that as the critical temperature 

 is approached the vapor begins to conduct freely, while the 

 liquid changes its electrical character to a much less extent. 



(5) The conductivity of saturated arsenic vapor at a bright red 

 heat is of the same order as that of mercury, and obeys Ohm's 

 law, at all events up to an electromotive intensity of more than 



100 volts per cm. — Phil. Mag., Nov., 1902, pp. 596-605. j. t. ^ 



11. Ionization of Nuclei Produced by Violent Agitation of 

 Dilute Solutions ; communicated by C. Baeus. — Discharging the 

 nuclei produced by violent agitation of dilute solutions, in a steady 

 stream at once into a tubular condenser, the following deflections 



