July 23, 1915] 



SCIENCE 



131 



from Crowther's table, and in column iii are 

 given the corresponding values of A calcu- 

 lated by multiplying \/p by the densities in 

 the solid form of the corresponding elements. 

 Column iv contains the electrical density, D^, 

 calculated by dividing the atomic charges of 

 the elements by their respective atomic vol- 

 umes in the solid state, and column v contains 

 values X/Dg. It will be seen that the varia- 

 tions from a mean value are less in column v 

 than in column ii. This is also shown graph- 



Electrical lenslty Indloated By Circles, 

 llasa • n « Crosses. 



Fig. 1. 



ically in Fig. 1, where the mass densities and 

 the electrical densities are plotted against the 

 absorption coefficient. The points representing 

 the relations of the electrical densities to the 

 corresponding absorption coefficients are indi- 

 cated by circles, while the corresponding points 

 for mass densities are indicated by crosses. It 



will be seen that the circles lie more nearly 

 on a smooth curve than do the crosses. 



Fernardo Sanford 



Stanford Univeesitt, Calif. 



evidence proving that the belly river beds 



of alberta are equivalent with the 



judith river beds of montana 



On the twenty-fourth of last July a paper of 

 mine appeared in Science in which I took the 

 ground that the Dog Creek Beds of Montana 

 were equivalent to the Edmonton Beds of Al- 

 berta and that the Cow Island Beds of Mon- 

 tana should be correlated with the Belly Eiver 

 series of Alberta, with the Fort Pierre de- 

 posits between. I thus took the early views of 

 Professor E. D. Cope that the Judith Eiver 

 Beds were on top of the Pierre. Judging from 

 memory, I was unable to believe that the Fort 

 Pierre was on top of the Judith Eiver forma- 

 tion. I concluded, therefore, that the sequence 

 of rocks in Montana would be the same as 

 those in Alberta, where the Belly Eiver series 

 is below the Pierre, and the Edmonton is above. 



Last July, however, with Mr. D. B. Dowling, 

 a senior geologist of the Geological Survey of 

 Canada, and my son, Charles M., who took 

 most of the photographs, I spent ten days in 

 the Judith Eiver country, going over the same 

 region I walked over in 1876 as Professor 

 Cope's assistant. I was soon forced by incon- 

 testable evidence to change my opinions, and 

 accept without reservations the conclusions of 

 Hatcher and Stanton in their fine work on the 

 " Geology and Paleontology of the Judith 

 Eiver Beds." We actually added to the weight 

 of the evidence they had gathered by the dis- 

 covery, as I believe for the first time, of some 

 sixty feet of Bear Paw shales on top of the 

 Judith Eiver Beds, on the head of Taffy 

 Creek, an easterly fork of Dog Creek. Also 

 heavy masses on top on the south side of the 

 river near Cow Island. Mr. E. G. McConnell, 

 deputy minister and director of the Geological 

 Survey of Canada, has kindly allowed me to 

 present this paper in a private capacity, Mr. 

 Dowling being the mouthpiece of the Geolog- 



