12 Prof. D. B. Brace on Negative Results of 



indicate a complete correspondence, to all orders, of the 

 molecular phases in the moving and in the fixed systems. 



On the other hand, Lorentz * has shown in his analysis for 

 " electromagnetic phenomena in a system moving with any 

 velocity smaller than that of light " that, with the aid of the 

 contraction-hypothesis, many electrical and optical effects 

 will be independent of the motion of the system for all 

 orders. This assumption of a shrinkage, although bold and 

 thus far entirely hypothetical, is not impossible, and is the 

 only suggestion yet made which is capable of reconciling the 

 negative results of second and third order experiments with 

 a quiescent aether. Poincaref has raised objection to the 

 electromagnetic theory for moving bodies, that each time new 

 facts are brought to light a new hypothesis has to be intro- 

 duced. This criticism seems to have been fairly met by 

 Lorentz in his latest treatment of the subject. The deductions, 

 however, from his theory make it untenable without further 

 development. The physical consequences, at least, seem at 

 present to be beyond experimental examination. So far no 

 valid reasons have been brought forward which necessitate 

 the shrinkage hypothesis in the electromagnetic theory. In 

 this connexion, reference should be made to the proof which 

 Hasenohrl J, reasoning from a cyclic process in a moving- 

 radiating system, has given, that the second law of thermo- 

 dynamics is contradicted unless either a second order con- 

 traction takes place in the direction of drift or the emission 

 varies with the velocity, which latter he considers impossible. 



On the other hand, Abraham § finds, neglecting fourth and 

 higher order quantities, the ratio of the transverse to the 

 longitudinal mass of the moving electrons to be 



while Lorentz requires the ratio to be 



for perfect compensation : thus leaving a double refraction of 

 the order - 1 ^ J to be accounted for, which would have been 

 detected several thousand times over in my experiment. The 



* Amsterdam Proc. April 1904, p. 809. 



t Rapports du Congres de Physique de 1900, Paris, i. pp. 2'2, 23. 



X Annalen, Band xiii. p. 367. 



§ Annalen, Band xiv. p. 236. 



