Mr. F. Guthrie on Approach caused by Vibration. 41 



a funnel 0*2 m. in diameter. The neck of the funnel was placed in the 

 mouth, and the drum of the funnel was brought opposite and parallel to 

 the edged face of the paper drum. Air was rapidly forced into and drawn 

 out of the funnel. The paper drum moved towards the funnel even from 

 a distance of 0*1 m. 



§26. Experiment 12. — A sheet of cardboard 0*4 m. square was hung 

 in the plane Vfrom a rod I'O m. long. The cardboard was counterpoised, 

 and hung from a silk tape. The paper drum of § 25 was placed 0'05 in. 

 from the cardboard, and parallel to it, and was then thipped. The card- 

 board moved towards the drum. 



§ 27. Experiment 13. — A rod of brass 1*2 m. long, provided at the ends 

 with disks of brass perpendicular to the rod 0*26 m. in diameter, was set 

 in longitudinal vibration by means of resined leather. One of the disks 

 was held, during the vibration, near to the cardboard of § 26, also near the 

 cotton-wool and muslin of § 24. In all cases the suspended body moved 

 towards the disk. By this means it was easy to cause motion when the 

 two were at the distance of 0*2 m. 



§ 28. I have in the foregoing paragraphs sought to eliminate systema- 

 tically secondary and disturbing influences from the fundamental experi- 

 ment. The experimental results appear to me to point to the following 

 conclusions. 



Whenever an elastic medium is between two vibrating bodies, or between 

 a vibrating body and one at rest, and when the vibrations are dispersed in 

 consequence of their impact on one or both of the bodies, the bodies will 

 be urged together. 



The dispersion of a vibration produces a similar effect to that produced 

 by the dispersion of the air-current in Clement's experiment, and, like the 

 latter, the effect is due to the pressure exerted by the medium, which is in 

 a state of higher mean tension on the side of the body furthest from the 

 origin of vibration than on the side towards it. 



In mechanics, — in nature there is no such thing as a pulling force — 

 though the term attraction may have been used in the above to denote the 

 tendency of bodies to approach, the line of conclusions here indicated 

 tends to argue that there is no such thing as attraction in the sense of a 

 pulling force, and that two utterly isolated bodies cannot influence one 

 another. 



If the setherial vibrations which are supposed to constitute radiant heat 

 resemble the aerial vibrations which constitute radiant sound, the heat 

 which all bodies possess, and which they are all supposed to radiate in ex- 

 change, will cause all bodies to be urged towards one another. 



