830 



SCIENCE 



[N. S. Vol. XXIX. No. 751 



(fishes, mussels), and since all creatures belong- 

 ing to the ecological community of the fresh- 

 water are mutually dependent upon each other, 

 it is very desirable that the causes which lead to 

 the destruction of fresh-water life should be re- 

 moved. 



These causes are: direct extermination by man; 

 pollution of the streams ; and river " improve- 

 ments," as, for instance, the building of dams. 

 The pollution of the water is the most important 

 cause, and, in western Pennsylvania, it is chiefly 

 the coal mining and the oil industries which have 

 contributed to the deterioration and destruction 

 of the fresh-water fauna. 



The extent to which this contamination of the 



waters has been carried in western Pennsylvania 



was clearly laid down on a map. 



The Stratigraphic Position of the Oolitic Iron-ore 



at Bloomslurg, Pa.: Gilbebt Van Inqen, of 



Princeton. 



A study of the so-called " Clinton fossil iron 

 ores " in the vicinity of Bloomsburg, Pa., shows 

 that these oolitic areas are above the Shawangunk 

 grit and conglomerate which is Lower Salina in 

 age, and that they are certainly above the Lower 

 Salina. They contain an extensive fauna and the 

 paleontological evidence points to a Salina age, 

 at least post-Clinton and post-Niagara. 

 A Mechanical Device for the Tabulation of the 

 Sums of Numerous Variable Functions: Pro- 

 fessor Ebnest W. Bbown, of New Haven. 

 On Certain Generalizations of the Problem of 

 Three Bodies: President Edgae Odell Lovett, 

 of Houston, Texas. 

 Penrose's Graphical Method of Orbit Computa- 

 tion: Mr. Ebic Doolittle, of Philadelphia. 

 The method shows how, when the exact position 

 of a moving comet or planet among the stars has 

 been observed on three or more nights, the path 

 of the body can be determined and also the posi- 

 tion which the body will occupy as viewed from 

 the earth at any desired time. But little com- 

 putation and no knowledge of higher mathematics 

 is necessary in applying the method which well 

 illustrates the principles of more intricate meth- 

 ods and also enables the position of the body in 

 the sky to be predicted with sufficient accuracy 

 to render it easily found in a telescope at any 

 time. 



On the Remarkable Changes in the Tail of Comet 

 C. 1908 (Morehouse), and on a Theory to 

 Account for these Changes: Professor E. E. 

 Baenabd, of Yerkes Observatory, Williams Bay, 

 Wis. 



Professor Barnard exhibited a remarkable series 

 of photographs made with the photographic tele- 

 scopes at the observatory, showing changes that 

 occurred in the tail of this comet which appear 

 to indicate resistance to the passage of the body 

 through space. In discussion of the paper it was 

 suggested that this resistance might arise from 

 clouds of meteoric dust, too fine to be visibly 

 appreciable, but which might still be dense enough 

 to ofi'er a resistance that would account for the 

 changes in the form of the tail of the comet that 

 were shown by the photographs. 

 The Past History of the Earth as Inferred from 



the Mode of Formation of the Solar System: 



Dr. T. J. J. See, of U. S. Naval Observatory, 



Mare Island, Cal. 



Linear Resistance between Two Parallel Conduct- 

 ing Cylinders: Professor A. E. Kennelly, Har- 

 vard University, Cambridge, Mass. 

 The equipotential surfaces perpendicular to the 

 lines of flow between two equally and oppositely 

 charged parallel wires of very small radii are 

 cylinders whose axes are in the plane of and paral- 

 lel to the charged wires. If any of these cylinders 

 were made conducting and the charge on the wire 

 within transferred to it, the lines of flow and 

 equipotential surfaces on the outside would re- 

 main the same. Hence the resistance between any 

 two such cylinders can be expressed in terms of 

 their radii and the distance between their centers. 

 The equivalent linear resistance between two equal 

 cylinders or of one cylinder and the medium plane 

 may be simply expressed as a product of its cir- 

 cumference and a function of its radii and the 

 distance of its center from the plane. 



Vacuum Effects in Electrical Discharge around a 



Right Angle in a Wire: Professor Fbancis E. 



NiPHEB, of St. Louis. 

 On the Ruling of Diffraction Gratings: Professor 



Albeet a. Michelson, University of Chicago, 



111. 



The paper gave a brief statement of the develop- 

 ment of the grating, mentioning the ingenious 

 wire grating of Fraunhofer, the improvements of 

 Rutherford, and the magnificent gratings of Row- 

 land. These were sufiicient in their day, but prob- 

 lems connected with more recent researches like 

 the Zeeman efi'ect and phenomena of that nature 

 demanded a much greater resolving power. In 

 this connection it was pointed out that the im- 

 portant fact was not so much the number of 

 rulings per inch as the total number of rulings, 

 and that this greater number of rulings necessi- 



