24 



SCIENCE 



[N. S. Vol. XLIV. No. 1123 



rived; also by aid of (4) and Newton's third 

 law, that " action and reaction are always 

 equal and contrary " the problem of impact of 

 two particles can be solved. 



8. By pursuing the course outlined above, 

 the student has to learn and thoroughly under- 

 stand, only two simple formulas, M = W/g, 

 F=Ma, "Wm. Cain 



Chapel Hill, N. C. 



GRAVITATION AND ELECTRICAL ACTION 



In a paper to be published by the Academy 

 of Science of St. Louis, evidence will be pre- 

 sented which appears to show conclusively, that 

 gravitational attraction is diminished by elec- 

 trical charges on the acting masses. The sus- 

 pended masses of the Cavendish experiment 

 are wholly enclosed in a shield of sheet metal. 

 The small observation window is covered with 

 wire gauze. When a knob terminal connected 

 with the influence machine is moved towards 

 or away from a knob terminal connected with 

 the large attracting masses, the suspended 

 masses slowly move to and fro around the 

 vertical line of suspension. No disruptive 

 discharges occur. It is found that gravita- 

 tional attraction is decreased by either posi- 

 tive or negative electrification. By the to-and- 

 fro movement of the knob terminal, the ampli- 

 tude of vibration can be gradually increased 

 from 2.5 minutes of arc to 50 minutes. It has 

 been established by experimental methods that 

 these results are not due to heat effects. 



- Francis E. Nipher 



THE PRODUCTION OF RADIUM 



To the Editor op Science : On page 799 of 

 the June 2, 1916, issue of Science a statement 

 is made in regard to the production of radium 

 by the Standard Chemical Co. in the year 

 1915, which is not in accord with facts, and I 

 wish to make this correction. The actual 

 amount of radium produced by the Standard 

 Chemical Co. during 1915 was slightly more 

 than 3 grams of radium element and of this 

 the larger proportion was produced in the first 

 three months of the year from radium which 

 was in process of treatment during the latter 

 part of 1914. 



In this same article the production of ra- 



dium at a cost of $37,599 per gram by the Na- 

 tional Radium Institute Inc. working in co- 

 operation and under the supervision of the 

 Bureau of Mines, is compared with the market 

 price of radium of $120,000 a gram. The 

 radium produced by the National Radium In- 

 stitute was obtained from high-grade earnotite 

 ore treated without concentration, and the cost 

 of production under these conditions is not 

 properly comparable to the cost of production 

 or the selling price of radium from lower 

 grade ore or concentrates. 



Applying the Bureau of Mines process to 

 unconcentrated ore containing about 1.5 per 

 cent, of uranium oxide (which is higher than 

 the average earnotite ore) makes the cost of 

 production nearer $70,000 than $40,000 per 

 gram. Since this is practically the condition 

 under which commercial producers of radium 

 must operate, it would be fairer to compare 

 cost of production by the Bureau of Mines 

 process on this basis, rather than on the basis 

 of the uncommercial and somewhat artificial 

 conditions, connected with the treatment of 

 the 1,000 tons of high-grade ore. Concentra- 

 tion of the low-grade ore, if practised, natu- 

 rally reduces the efficiency of extraction, and 

 in this way would raise the cost of production. 



"While it is true that the war cut off prac- 

 tically the entire European market to radium 

 producers, it must be added that the growing 

 American market for radium has been very ad- 

 versely influenced by the widespread publish- 

 ing of statements, from the United States 

 Bureau of Mines, similar to the statement in 

 Science which we are criticizing. The general 

 effect of these statements has been to lead pros- 

 pective purchasers of radium to believe that 

 radium would soon be available at enormously 

 reduced prices. Emphasis being laid by the 

 Bureau of Mines on the exceptionally low cost 

 of production, and in general no mention be- 

 ing made of the fact that this low cost of pro- 

 duction was in a large measure due to the 

 abnormal and uncommercial conditions under 

 which the Bureau operated. 



As regards ore concentration it is also in- 

 teresting to note that the method used by the 

 Bureau of Mines is one which has been used 



