'844 Dr. C. V. Burton : An Experiment indicating 



region bounded by a fixed ideal surface and originally free 

 from atomic matter, a mass m of matter is introduced, Fm is 

 the volume of setber which flows outward across the bounding 

 surface "*. If p is the density of the sether, it is the quantity 

 ¥ 2 p which should be effective in producing forces between 

 bodies which are in motion through the sether, and from the 

 null result given by the observations an upper limit is assigned 

 to the value of F 2 p. 



3. This work was undertaken because it seemed by no 

 means self-evident that the property sought for must be 

 absent. If positive results had been obtained, the means of 

 determining our motion with respect to the sether would have 

 been to hand ; nor would such a result have been necessarily in 

 contradiction to the electromagnetic principle of relativity, the 

 •effects in question being outside the electromagnetic scheme. 

 But since no such effects were observed, those who uphold 

 the principle of relativity in its most absolute sense will find 

 nothing here to impugn their beliefs. 



4. It is shown in the sequel that if ¥ 2 p were finite, a flat 

 plate moving uniformly in a given direction through the 

 aether would tend to set itself with its plane perpendicular to 

 that direction, being acted on by a couple whenever its normal 

 was oblique to the line of motion f . Accordingly the most 

 ^convenient way to test for the existence of the effects now in 

 question is to suspend such a plate by a fine fibre so that its 

 plane is vertical, and to watch for any changes of azimuth 

 which may occur as the earth's rotation causes the suspended 

 system to be presented in varying aspects to the earth's line 

 of motion. 



Experimental Arrangements. 



5. Observations were made with two different suspended 

 plates, each of 5 per cent, iridio-platinum. The first plate 

 had tbe form and dimensions indicated in fig. 1. The tail 

 served as a point of attachment for the suspending fibre ; it 

 was integral with the plate, and was much thinner than 

 the main portion, one side of which was optically polished. 

 The second plate (fig. 2) was of simple rectangular form, and 

 had near its top end a minute hole through which could be 



* Loc. tit, 



i_ There is thus a certain analogy to the case of a laminar solid moving 

 bodily through a frictionless liquid ; but the analogy is by no means close. 

 We are here concerned with the actions exerted between the sether and 

 the nuclei and electrons of which a material plate is made up ; we 

 suppose that the motion of these through the aether is simply a question 

 of strain-transference, and involves nothing of the nature of a gross bodily 

 displacement. 



