474 



SCIENCE. 



[N. S. Vol. XVI. No. 403. 



variance with Ameghino's. When he places 

 the marine Cretaceous beds of the lower Rio 

 Tarde section in the Neocomian, while Stanton 

 declares them not older than Gault, and when 

 he places the marine Patagonian beds in the 

 Eocene, while I assign them to the Lower 

 Miocene, he can do so only if he introduces 

 new evidence, and shows that our determina- 

 tions are incorrect. But he has not done this, 

 and has never attempted to do it, and there- 

 fore his personal opinion on this question is 

 without any scientific value. 



Ameghino may claim that my final report 

 on the Tertiary invertebrates had not come 

 into his hands when he wrote the present paper. 

 But he must have seen Stanton's report, as 

 well as the preliminary notes by Hatcher and 

 myself in the American Journal of Science. 

 These should have induced him to wait for the 

 publication of my final report. 



Dr. a. E. Ortmann. 



Princeton University, 

 September, 1902. 



VELOCITY OF LIGHT IN AN ELECTROSTATIC FIELD. 



To THE Editor of Science: In a paper, 

 ' Determination of the Electric and Magnetic 

 Quantities,' Phys. Rev., January, 1900, I 

 pointed out that light should be accelerated in 

 an electrostatic field. I have to announce that 

 preliminary experiments made last year show 

 that this is the case, though the velocity ac- 

 tually observed is only eighty per cent, of that 

 predicted in the paper referred to. 



The tests, however, were rough and can be 

 made more accurately with improved apparat- 

 us. I am desirous of repeating them, and ob- 

 taining a closer result. I would be glad to 

 know of any one who has worked on inter- 

 ference phenomena who would be willing to 

 collaborate with me, I of course bearing all 

 expense. 



In a recent note to the Toronto Astronom- 

 ical Society, I refer to a paper to be published 

 in Science, in which I show that by a develop- 

 ment of the vortex theory described in the 

 above-mentioned paper, the difference between 

 positive and negative electricity is explained. 

 By some mishap this paper was lost in the 



mails, about last December, and merely the 

 letter forwarded with it reached the editor. I 

 hope to rewrite it, but at present would say 

 that I found that the difference is merely one 

 of circulation, i. e., that the simple vortex 

 singularity must be taken as the negative 

 electron, and that when a number of the vortex 

 singularities are so grouped that their circu- 

 lation is closed, they behave as positive elec- 

 trons. Hence the positive electron is simply 

 an agglomeration of negative electrons, sO' 

 grouped as to have a closed circulation. 



Reginald A. Fessenden. 



SHORTER ARTICLES. 



THE FORM.ATION OF DEWBOWS. 



If an observer standing on a mountain top 

 should view below him, under suitable con- 

 ditions, a horizontal stratum of falling rain- 

 drops on which the sun was shining, he would 

 see a rainbow. This bow would appear as a 

 true circle, or a segment of it, depending upon 

 the area of the stratum and the position of the 

 sun. If, however, he could view this bow 

 with reference to its space relations, he would 

 no longer see a circle, but some other conic 

 section. This latter condition was recently 

 observed to be satisfied by the reflection and 

 refraction of sunlight in the drops of dew on 

 a lawn. The phenomenon appears to be 

 unique, and furnishes another interesting- 

 modification of the familiar rainbow. 



The space in front of one of the Government 

 buildings had been recently harrowed and 

 then carefully leveled and rolled, and finally 

 seeded thickly with Kentucky blue grass. At 

 the time the observations were made this 

 grass was about one and a half centimeters 

 high, covering the ground thickly, and very 

 uniform in height, the fine spears being sur- 

 mounted with drops of dew. 



On standing with one's back to the sun, one 

 could see the bow on the grass very distinctly, 

 which at nine o'clock a.m. was at a distance of 

 about one meter at its nearest point, and then 

 extended on either side in the form of a conic, 

 to a distance of from ten to fifteen meters. 

 The red color of the outer portion of the bow 

 and the blue of the inner side were well de- 



