470 



SCIENCE 



[N. S. Vol. XXIX. No. 742 



Photographs of the arc and spark spectra of 

 Ca, Sr and Ba, taken with a quartz spectrograph, 

 show several new ultra-violet lines. In Ca a new 

 spectrum series was found, consisting of reversed 

 single lines, beginning with X 2398, eight lines in 

 all being observed, five of them new. In Sr a 

 similar series exists, seven lines having been ob- 

 served. In Ba there are evidences of the same 

 sort of thing. Series of pairs have been known 

 for some time to exist in these spectra; few of 

 the lines, however, having been picked up. Four 

 new pairs were found in Ba and two in Sr, which 

 help to fill out the two " subordinate " pair series 

 in each of these elements. Formulae which repre- 

 sent these series were calculated out, as was also 

 done in the case of the series first mentioned. 



Ionization in Closed Vessels: W. W. Stbong, 

 Johns Hopkins University. 

 The purpose of these experiments is to find 

 what the nature of the external radiations are, 

 that produce part of the ionization in closed ves- 

 sels. In order to do this it is necessary to use a 

 vessel in which the ionization produced by the 

 walls of the vessel itself is constant. This ioniza- 

 tion can be easily found by putting the vessel 

 within a thick screen of metal or water so that 

 all external radiations are absorbed. 



Electroscopes were used for this work and the 

 ionization of the enclosed gas was measured by 

 means of the rate of leak of the electricity from 

 the gold-leaves suspended inside the electroscope. 

 The charged system inside the electroscope could 

 be charged from the outside by means of a small 

 spark gap. The electroscope was, therefore, air- 

 tight and everything inside the vessel remained 

 the same unless aflfected by radiations that could 

 pass through the walls of the electroscope. 



By letting the electroscope into a large cistern 

 it was surrounded by a screen of water at least 

 four feet thick. This was done with an electro- 

 scope September, 1907 {Phys. Rev., p. 44, July, 

 1908). The same electroscope was placed in the 

 same cistern, July, 1908. (Readings of the electro- 

 scope were here given.) 



These readings show that the natural ionization 

 within the vessel had remained practically con- 

 stant throughout almost a year. 



The same electroscope (and others in a like 

 manner) when placed outside of buildings showed 

 very marked increase in its rate of leak during 

 the day. This, therefore, must be due to some 

 external radiation that was screened off by the 

 water in the cistern. (Screens of lead and iron 



were also used.) Care was taken to keep the 

 temperature of the electroscope constant. 



Velocity of the Negative Ions Produced hy the 

 Ultra-violet Rays in Various Oases at Differ- 

 ent Pressures and Temperatures: Alois F. 

 KovabIk, University of Minnesota. 

 The object of this investigation is the study of 

 the structure of the negative ion. For this pur- 

 pose the velocity is measured at difi'erent pres- 

 sures and at different temperatures. The method 

 used is that of an alternating field. In the case 

 of air the product of the velocity by the pressure 

 is nearly constant between the pressures 760 mm. 

 and 200 mm., but at 100 mm. this product in- 

 creases by 25 per cent., at 60 mm. by 65 per cent, 

 and at 4.3 mm. by 200 per cent, above the value 

 at 760 mm. In the case of COj the product 

 changes a little more rapidly. The Telocity of 

 the negative ions in dry air at 760 mm. and 0° C. 

 is 2.05 cm. per second for a gradient of 1 volt per 

 centimeter, and in dry COi at ordinary conditions 

 of pressure and temperature, the vejocity is about 

 1.02 cm. per sec. 



Preliminary experiments with change of tem- 

 perature were made in air and up to 400° C. the 

 velocity was found to vary inversely as the den- 

 sity of air. These experiments are being con- 

 tinued. 



Momentum Effects in Electrical Discharge: F. E. 

 NrPHER, Washington University. 

 An electrical discharge is sent around a right 

 angle in a wire. Spark discharge passes from 

 machine to earth in either the positive or nega- 

 tive line. 



A very marked difference between the positive 

 and the negative discharge is found. A decided 

 difference between the effects on the photographic 

 plate is foimd on the two sides of the angle. 

 The negative discharge is the active one in both 

 lines. An account of these experimental results 

 is given in Science for December 4, 1908. The 

 actual effects were shown by means of a large 

 number of lantern slides. 



Electrical Stimulation ^of Plant Growth: Amon 

 B. Plowman, Beaver, Pa. 



Experiments and observations extending through 

 a period of more than ten years, indicate rather 

 conclusively that electrical charges of positive 

 sign more or less completely inhibit the vital 

 processes of plant protoplasm through which 

 such charges are caused to pass; while, within a 

 rather wide range of conditions, negative elec- 

 trical charges stimulate such processes, some- 

 times to a quite remarkable degree. 



