306 



SCIENCE 



[N. S. Vol. LIV. No. 1396 



as before. The fiber was not injured by the 

 discharge but could be saturated and used 

 again and again. About the same number of 

 discharges as had been employed with the ex- 

 ploded wires produced satisfactory results. 

 For convenience in discussion and because of 

 its character this new light source has been 

 tentatively called the super spark. 



An inspection of the calcium spectrum thus 

 produced showed a striking enhancement of 

 the spark lines of calcium over the arc lines 

 indicating that a large proportion of the 

 emitting atoms were ionized. For the pur- 

 poses of comparison a table is inserted show- 

 ing for the present work with the exploded 

 wire and super-spark and for the work of 

 other observers with various sources — the 

 relative intensities of the H and K lines of 

 calcium, a prominent spark doublet, and the 

 line 4227, a strong arc line. The ratio of 

 these intensities is, we believe, a fair index 

 of the relative proportions of ionized and un- 

 ionized emitting atoms in the source. 



THE RELATrVE DEGREE OP IONIZATION OF CALrJIUM IN 

 DIFFERENT SOURCES 



King's electric furnace 



Crew & McCauley arc 



Lockyer spark 



Loving vacuum arc 



Exploded wire 



Super spark 



High chromosphere of sun . 

 Class B stars 



1:19 

 4:5 

 5:4 

 5:2 

 4:1 

 10:1 

 9:1 

 7:1 



This table indicates that there can be pro- 

 duced in the laboratory the same degree of 

 ionization as is shown to exist in the high 

 chromosphere of the sun or in the spectra of 

 the early (or hot) type B stars. The super 

 spark seems to give a more highly ionized 

 source than any yet produced in the labora- 

 tory. 



The results of an extended study soon to be 

 published of the super spark spectra of cal- 

 cium and other metals may be briefly sum- 

 marized here. For the metals studied in the 



groups one, two and three of the periodic table, 

 an almost pure enhanced line or spark spec- 

 trum has been produced. As might be ex- 

 pected it has been impossible to get perfect 

 ionization even in this source and the strongest 

 lines due to the neutral atom still persist. A 

 striking feature of the super spark is the amaz- 

 ingly small amount of material required to 

 produce spectra. By use of a dilute solution 

 of calcium chloride for example there is pro- 

 duced not only the calcium spectrum but also 

 the spectrum of the other metals of the same 

 group: Magnesium, barium, strontium, zinc 

 and cadmium; and generally a few lines of 

 other metals. These other metals could have 

 been present only in minute amounts and yet 

 their spectra rival in intensity that of the 

 principal substance. Another striking charac- 

 teristic is that practically only metallic lines 

 are produced by the super spark, — the spectra 

 of hydrogen, oxygen or of the acid radical of 

 the salt used do not appear, and only the 

 strongest air lines can be identified. 



The super spark, it will be seen, gives a 

 method by which a very powerful stimulus 

 can be applied to any metal that can be 

 obtained in the form of any of its partially 

 soluble salts. It is not even necessary that 

 the metal in question be the principal metal- 

 lic constituent of the salt. Good results may 

 be obtained for metals which appear only as 

 minor impurities in the salt used. 



E. A. Sawyer, 

 A. L. Becker 

 Physical Laboratory, 

 University of Michigan, 

 August 11, 1921. 



THE IOWA ACADEMY OF SCIENCE 



The thirty-fifth annual session of the Iowa 

 Academy of Science was held at Simpson College, 

 Indianola, on April 29 and 30. At the opening 

 meeting on Friday afternoon President Knight 

 gave his presidential address on "American 

 science. ' ' The Academy divided into sections of 

 botany, zoology, geology, and physics for the read- 

 ing of papers, and at 5 o'clock adjourned for an 

 enjoyable auto ride given by the Indianola Cham- 

 ber of Commerce. At 6 o 'clock the sections met 

 for group dinners and at 8 o 'clock Dr. J. Paul 

 Goode of the University of Chicago, addressed the 



