252 Intelligence and Miscellaneous Articles. 



The text has been very carefully drawn up and should be useful 

 for young teachers. The distinction between the signs of operation 

 and the signs of quality is very clearly indicated by means of a 

 special notation. There is a good chapter on the interpretation 

 of the solutions of Problems, such questions as that of the problem 

 of the couriers and allied problems being worked out in some 

 detail. In some few places one would have expected the Authors 

 to have been a little fuller, but the general level is high. The 

 exercises are very numerous and well graded. The number is 

 intentionally large " that the teacher from year to year may have 

 Variety with different classes." There is no mention of Graphs, a 

 branch of the subject which Prof. Chrystal's book brings into 

 prominence. The book can be resommend^d as a sound treatise 

 on the elements of Algebra, and the printers have done their work 

 well. The most important typographical error we have come, 

 across is on p. 611 line 5, where for " first" read " second." There 

 are no answers at the end. 



XVIII. Intelligence and Miscellaneous Articles. 



RELATIVE MOTION OF THE EARTH AND .ETHER. 

 To the Editors of the Philosophical Magazine. 

 Gentlemen, 



IN your September number Dr. Lodge comments on my objection 

 to the conclusiveness of the Michelson-Morley aether experi- 

 ment, and I should like to point out that his remarks are founded 

 on a strange misconception of the nature of my objection. He 

 conjectures that I attribute the negative result of the Michelson 

 and Morley experiment " to the possible second-order influence of 

 a hitherto neglected first-order tilting or shifting of the wave-fronts 

 brought about by the undiscovered drift of the aether past the 

 earth." But in my communication I pointed out that nay objection 

 was not of this nature, but related to the assumption made as to 

 the optical sensitiveness of the system of interference-fringes 

 relied ou by the experimenters to enable them to measure the 

 minute length in question in their experiments. My contention 

 was simply that the system of fringes used in the experiment had 

 probably a more complex character than was supposed, and that 

 therefore its capability of measuring the small length accurately 

 was over-rated to an unknown extent. Evidently Dr. Lodge has 

 pondered so deeply on aberration problems that in reading my 

 paper his thought has got into sone old groove which he has 

 unconsciously taken to be the direction of my argument. 



Yours obediently, 



William Sutherland. 



Postscript by Prof. Lodge. — I was not very clear about Mr; 

 Sutherland's precise line of argument, nor am I now ; but there 

 was an imaginary loophole which others might attempt to get 

 through, though Mr. Sutherland, as it now appears, did not; and 

 I took the opportunity (not specially opportune as it turns out) of 

 indicating that it was closed. 



