Janl'abt 18, 1918] 



SCIENCE 



71 



formed of hemispherical envelopes of vapor, which 

 rise from the nucleus itself, dissolve themselves in 

 the coma, and are gradually repelled from the sun 

 so as to form the material of the tail. 



The turning point in the motion of these 

 dust particles which are repelled towards the 

 sun may be thus defined. The gravitational 

 repulsion of the nucleus, the gravitational 

 attraction (or repulsion) of the sun, and the 

 repulsion due to the pressure of light-waves, 

 are balanced against each other. These dust 

 particles are gradually dispersed into space. 

 The radiation of negative corpuscles from the 

 Sim, superposed upon tiie other causes above 

 mentioned, seems to furnish a full explanation 

 of the phenomena of the comet. 



Francis E. Nipher 



barite in georgia 

 In the Friday, December 21, 1917, issue of 

 Science, on page 611, under the title of 

 "Chemical industries of the United States," 

 you quote from the annual report of Franklin 

 K. Lane, Secretary of the Interior, 



Before the war 40,000 tons of barite were im- 

 ported from Germany for the manufacture of 

 lithopone. Now five companies are producing this 

 article from deposits in Tennessee, Kentucky, Vir- 

 ginia and Missouri. 



This quotation is incorrect in that over 50 

 per cent, of the barite produced in the United 

 States comes from deposits near CartersviUe, 

 Georgia. There are three companies in the 

 CartersviUe district that have produced over 

 20,000 tons apiece during 1917, while the total 

 output from this dictrict could be conserva- 

 tively estimated at 75,000 tons during 1917. 

 You do not mention that any barite at all is 

 mined in Georgia, and I feel that this should 

 be brought to the attention of the public, as it 

 is an injustice to this mining district, as they 

 are the largest producers of this mineral in the 

 United States. Wilbur A. Nelson 



Cartebsville, Ga. 



manganese in alberta 

 Mv attention has been directed to an article 

 in Science, January 4, 1918, page 20, describ- 



ing a large deposit of manganese occurring in 

 the Cypress Hills, Alberta. Permit me to say, 

 through the medium of your valuable maga- 

 zine, that the Geological Survey has no in- 

 formation regarding a deposit of the nature 

 described. During the summer of 1917 an ex- 

 amination was made by a member of the staff 

 of the Geological Survey of a deposit of low- 

 grade manganese in the Cypress Hills about 55 

 miles from Maple Creek and 15 miles from 

 Govenlock station on the Canadian Pacific 

 railway. Three samples gave on analysis 8.24, 

 18.45 and 17.59 per cent, of managanse. A 

 shipment of 500 pounds of the material was 

 tested in the Ore Dressing and Metallurgical 

 Laboratories of the Mines Branch and the con- 

 elusion was reached that it is of too low a 

 grade to be worked economically under present 

 conditions. 



"WiLLiAii McInnes, 

 Directing Geologist 



SCIENTIFIC BOOKS 



Studies on the Variation, Distrilution, and 

 Evolution of the Genus Partula. The Spe- 

 cies Inhabiting Tahiti. By H. E. Cramp- 

 ton. Carnegie Institution of Washington. 

 1916. 



This work has an interest for the student 

 of evolution in any group, quite apart from 

 its special interest to the conchologist. Such 

 variable non-mobile land shells scattered 

 widely among oceanic islands offer a field in 

 many aspects most favorable for compilation 

 of statistics bearing on speciation. Also, a 

 very large series of material has been studied 

 and adequately described and figured. 



Evolutionary writers frequently attempt to 

 balance an imposing structure of hypothesis 

 on a few inadequate facts. The paper under 

 discussion seems to have gone to the other 

 extreme in laying the Partula variation 

 almost entirely to the innate tendency to vary. 

 The statement that " the originative influence 

 of the ' environment ' seems to be little or 

 nothing" (p. 12) is perhaps justifiable, but 

 that " isolation proves to be a ' condition ' 

 and not a ' factor ' in differentiation of forms 

 belonging to this genus " is weakened when we 



