Junes, iSS8.] 



SCIENTIFIC NEWS. 



531 



yields to the more powerful, and is continually drawn 

 towards the free surface of the water. 



Hence it is unnecessary to assume the existence of a 

 repulsive force of an unknown nature, since we know that 

 there exists an attractive force which cannot remain 

 ineffective, i.e., the difterence between a strong attraction. 



effects. Even vapours show the result, and if air charged 

 with these vapours be drawn into a capillary tube, which 

 is then plunged into water, the level will be lowered in a 

 noticeable manner (Fig. 2). We perceive that the 

 effect is produced by vapours of camphor. Hence 

 we may foresee that this body will set the boat in 



Fig. I. — Tin Boat Moving on Water owing to Action of a Lump 

 OF Camphor in the Stern. 



Fig. 2. — Levels to which Water 

 Rises in Capillary Tubes filled re- 

 spectively WITH Air, a, Ether (E), 

 and Camphor (C). 



-Movement of Fine Grains of Camphor 

 THE Surface of Mercury. 



Fig. 4.— Tin Boat, 



AS IX Fig. i, Turning 

 Float. 



A Heavily-weighted 



that of the water, and a feeble attraction, that of the 

 alcohol. This fact is absolutely general. Ether, chloro- 

 form, the essences and the oils all produce a more or 

 less rapid movement of the boat. 



It might be expected that these effects would only be 

 produced with a considerable stratum of the liquid 

 superimposed upon the water. But on the contrary, a 

 very slight layer is sufficient to produce considerable 



motion like the liquids above-mentioned. The boat is 

 not merely set in motion, but it keeps up a rapid and 

 regular movement for hours. This experiment is very 

 easy, and it may be made visible to an audience by 

 fixing a mast (a straw) upright in the boat by means of 

 sealing-wax, a little streamer being attached to the 

 summit. 



The result is the same for mercury, upon which cam- 



