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



diameter, having a rim 0025 deep, was hung by a silk tape in 

 the same manner as the cylinder of § 32. Parchment was 

 stretched across the wide end of a funnel 0*20 metre 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 metre. 



§ 35. Experiment 15. — A sheet of cardboard 0*4 metre square 

 was hung in the plane V from a rod 1 metre long. The card- 

 board was counterpoised and hung from a silk tape. The paper 

 drum of § 34 was placed 005 from the cardboard and parallel to 

 it, and was then tipped. The cardboard moved towards the drum. 



§ 36. Experiment 16. — A rod of brass 1'2 metre long, pro- 

 vided at the ends with disks of brass perpendicular to the rod 

 026 metre 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 § 35, also near the cotton- 

 wool and muslin of § 33. 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 metre. 



§ 37. I have in the preceding paragraphs sought to eliminate 

 systematically secondary and disturbing influences from the fun- 

 damental experiment. 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 vibra- 

 tions 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 expe- 

 riment ; and, like the latter, the effect is due to the pressure 

 exerted by the medium, which is in a state of higher mean ten- 

 sion 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 occasionally 

 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 ra- 

 diant heat resemble the aerial vibrations which constitute radiant 

 sound, the heat which all bodies possess, and which they are 

 all supposed to radiate in exchange, will cause all bodies to be 

 urged towards one another. 



