94 



SCIENCE 



[N. S. Vol. XXVIII. No. 707 



proceeding from tlie plate grounded on the 

 water pipe. 



By the use of this grounded plate and by 

 replacing the thick hard-rubber cover of the 

 plate holder by a thin sheet of black paper, 

 in two eases distinct images have been pro- 

 duced by the positive discharge. In this case 

 only a few millimeters of air separated the 

 discharge wire from the film. It is then, 

 however, very difficult to prevent the electric 

 stresses from forming the branching images. 

 When this begins the results are quite uncer- 

 tain. When a negative discharge of the same 

 spark length is used under the conditions 

 which gave the faint positive image, the 

 image produced covers a couple of square 

 inches of plate. Five spark discharges of the 

 negative produce a much greater effect than 

 was produced by a hundred of the positive, 

 in the two cases when the latter discharge 

 produced any effect. The behavior of the 

 positive line is somewhat perplexing. An 

 X-ray tube will operate in this line, the 

 cathode being connected on the cylinder hung 

 in air. But these cathode particles do not 

 appear to be active at the angle. 



It may be possible to devise some method 

 of electrometer examination which will not 

 result in the destruction of the instrument. 

 The continuous current has not yet been ex- 

 amined. This, however, involves different 

 conditions from those existing in the circuits 

 here examined. There are many precautions 

 necessary in this work which can not be here 

 discussed, but which will be presented as soon 

 as final results can be given. It has required 

 the use of sixty dozen photographic plates in 

 order to reach the results already attained. 



It is evident that the effects here described 

 point to the action of the p and a " rays," 

 in radio-active phenomena. 



Francis E. Nipher 



dinichthys intermedius newberry froai the 

 huron shale 

 In the spring of 1907 Dr. Lynds Jones 

 found part of a dinichthyid mandible in the 

 Huron shale near Huron, Ohio, and the writer 

 collected it for the Geological Museum of 

 Oberlin College. The specimen includes all 



of the cutting blade of the mandible excepting 

 about one centimeter of the posterior end. 

 The length of the cutting blade is sixteen 

 centimeters. This indicates that the entire 

 length of the mandible was about thirty-five 

 centimeters. The width is eleven centimeters. 

 In size it agrees with mandibles of Dimchthys 

 intermedius Newb. and in form it agrees 

 closely with the same species, differing in the 

 greater and more regular concavity of the top 

 between the second cusp and the posterior end 

 of the cutting edge, and in the prominence 

 of the cusp-like projection between the an- 

 terior tooth and the main cusp. As pointed 

 out by Hussakof,^ the prominence of this 

 projection is probably an individual variation 

 and is not of specific value. In the writer's 

 opinion the first difference mentioned is not of 

 specific value. The denticles on the posterior 

 part of the cutting edge are smaller than in 

 .most specimens of Dimchthys interTnedius. 

 Teeth are absent from that part of the jaw 

 where they are prominent in Dinichthys 

 hertzeri. The differences between this man- 

 dible and those of Dinichthys iniermedvus are 

 so slight that the writer has no hesitation in 

 referring it to that species. The specimen is 

 important in demonstrating the presence of a 

 second species of Dinichthys in the Huron 

 shale and in showing that the type of mandible 

 of Dinichthys iniermedius and Dinichthys ter- 

 relli did not develop from the Dinichthys 

 hertzeri type. 



A figure of this specimen will be published 

 later with figures of other specimens recently 

 collected from the Huron shale. 



E. B. Branson 



Geological Department, 

 Obeblin College 



SOCIETIES AND ACADEMIES 



SOCIETY FOB EXPERIMENTAL BIOLOGY AND MEDICINE 



The twenty-eighth meeting of the society was 

 held in the physiological laboratory of the New 

 York University and Bellevue Hospital Medical 

 College, April 15, 190S. President Lee in the 

 chair. 



Members elected. — Otto C. Glaser, Alfred G. 

 Mayer, John B. Murphy, Isaac Ott. 



^Bull. Am. Mus. Nat. Hist., Vol. XXI., p. 411. 



