254 



SCIENCE 



[N. S. Vol. XXVIII. No. 712 



It is a fact noted by many investigators, 

 and especially insisted on by de Vries, that 

 most races' of domesticated species are de- 

 rived from the wild form by the loss of one 

 or more hereditary characters. That these 

 race peculiarities are, generally speaking, re- 

 cessive to the wild form is well established, 

 and the reason therefore is apparently clear. 

 But that these peculiarities may have origin- 

 ated ages ago in the wild form, and been 

 transmitted almost unnoticed, has not hitherto 

 been suggested. We have seen above that 

 such may be the case. Furthermore, peculiari- 

 ties that may have had indefinite time in 

 which to develop are not greatly in need of 

 a theory of " saltatory change " to explain 

 their abundant development in domesticated 

 species. 



W. J. Spillman 



U. S. Department of Agricultube 



TEE AMERICAN ASSOCIATION FOB THE 



ADVANCEMENT OF SCIENCE 



SECTION B—PHTSICS 



The summer meeting of the American Associa- 

 tion for the Advancement of Science, Section B, 

 was held in the Wilder Laboratory of Dartmouth 

 College, Hanover, N. H., June 30, 1908. This was 

 a joint meeting with the American Physical So- 

 ciety. There were two sessions, one in the fore- 

 noon and one in the afternoon. The attendance 

 at each was about seventy. Professor Edward L. 

 Nichols, president of the American Physical So- 

 ciety and president last year of the American 

 Association for the Advancement of Science, was 

 the presiding officer. 



The titles and abstracts of the sixteen papers 

 presented are given below: 



Light Pressure on Black Surfaces and on Thin 

 Plates of Glass (with experimental demonstra- 

 tion) : G. P. Hull, Dartmouth College. 

 Some years ago E. F. Nichols and Hull proved 

 the existence experimentally of a pressure due to 

 light upon a silvered glass surface. Maxwell had 

 proved theoretically that such a pressure exists. 

 By Larmor's theory, however, the pressure on 

 a glass surface should be zero. Professor Hull 

 showed experiments which do not justify Lar- 

 mor's conclusion. He exhibited an apparatus ia 

 action which showed the comparative effects ob- 

 tained by allowing radiation of the same intensity 

 to fall successively upon four kinds of surface. 



The results of such a comparison show the pres- 

 sures to be as follows: 



Deflection 



1 glass vane 1.0 



2 glass vanes 1.7 



Enclosed black vane 5.6 



Silvered vane 11.5 



These results indicate that Larmor's conclusion 

 is incorrect. Maxwell's formula gives results 

 quantitatively agreeing with the above measure- 

 ments. For example, the values indicated for 

 the above four cases by applying Maxwell's for- 

 mula are 1.0, 1.83, 5.86 and 11.2, respectively. 



(At the conclusion of the paper the president 

 of the Physical Society, who was presiding, con- 

 gratulated the section that all its members had 

 been able to see for themselves an effect due to a 

 force so small that the possibility of showing its 

 actual existence had not been hoped for by emi- 

 nent physicists until a very few years ago.) 



Changes in Density of the Ether, and Some Op- 

 tical Effects produced ly it: Chaeles F. 

 Bbtjsh, Cleveland. 



This paper described two series of careful ex- 

 periments, conducted on different lines, the re- 

 sults of which afford strong evidence in support 

 of the following hypotheses: 



1. The ether passes slowly, and not freely, 

 through glass and presumably through other 

 bodies. 



2. The ether is susceptible of change in density. 

 It may be dilated and presumably compressed in 

 a glass vessel, the phenomenon lasting long 

 enough to be observed with ease. 



3. While dilation of the ether does not alter 

 materially, if at all, the velocity of the light 

 waves in it, it does reduce the amplitude or 

 energy-carrying capacity of both long and short 

 waves, i. e., of low heat and actinic radiation. 



The apparatus and experiments were fully de- 

 scribed by means of a fine set of lantern slides, 

 many of which showed photographic effects ob- 

 tained during the experiments themselves. 



On Oscillations in the Metallic Arc: W. G. Cadt, 



Wesleyan University. 



Two types of oscillations occurring in an elec- 

 tric arc light were considered. The first are 

 produced in the iron arc in free air, with a fre- 

 quency of about 1,500 per second. These seem to 

 be mechanical and were dismissed with brief 

 comment. The second type was considered more 

 at length. They are of much higher frequency 

 and occur with electrodes of various substances. 



