Liquids on the Surface of Water. 47 



paper, I noticed a curious series of motions with the film of oil 

 of nutmegs that had been broken up by the action of creosote 

 and exposed some time to the air. The oil formed a well-defined 

 film with small bosses just within the edge ; and the film almost 

 completely covered the surface of the water in a shallow glass 

 3 inches in diameter. On placing a drop of creosote near the 

 edge, it entered the film and cleared out a space for itself, 

 although it did not vibrate as it usually does when alone on the 

 surface. It gradually flattened ; and as the film became thinner 

 by evaporation and displayed fine iridescent colours, the creo- 

 sote became active, broke up the film, and drove about the frag- 

 ments. When, however, the creosote was placed first on the 

 water and then the oil, the latter flashed into a film and stopped 

 the motions of the creosote ; but as the oil got thinner, the cre- 

 osote disks became active and cut through the film with energy. 

 One disk of creosote became attached to the edge of the glass 

 and exerted its influence chiefly in a right line nearly to the op- 

 posite point. Portions of the film, now become almost powdery 

 in texture, sailed up in gently curved lines to within one-tenth 

 of an inch of the creosote, and then fell-in in two and two, i. e. 

 one from either side of the creosote, and proceeded in a straight 

 line nearly to the opposite point with all the order and regularity 

 of a drill movement. This effect lasted about fifteen minutes, 

 until the creosote had nearly disappeared. When the oil was re- 

 distilled, it formed a smaller film than before ; a drop of creosote 

 shut it up instantly. When the creosote was put on the water 

 and then the newly distilled oil, the latter formed a lens. 



32. There are many curious phenomena which I noted down 

 during my study of cohesion-figures which could not well be 



with a chalky finger a pane of glass wet with condensed moisture, he noticed 

 that as the streams descended stained by the chalky particles, some of these 

 followed the descent, but others near the edge of the stream moved up- 

 wards. He then ground up a little oil with chalk or with a few drops of 

 water, and on leading a gentle stream of water into it down an almost 

 vertical plane, active contrary currents were obtained. In this case the 

 pure water reaching the oily deposit, its excess of tension over the oily 

 matter would tend to raise the superficial layer of oil and with it the solid 

 particles suspended in it. It seems to me, however, that, in such cases as 

 the above, other forces are at work as well as surface-tension. In refer- 

 ring to the phenomena of " tears in the wine-glass " as effects of a chemi- 

 cally clean surface (Phil. Mag. for October 1868), it is remarked that in 

 the spaces between the tears will be seen an ascending current " which 

 rises (1) by the adhesive action of capillarity, (2) by the formation of a 

 back current in consequence of the downward flow of the tears, just as a 

 backwater is formed at the place where two currents of a river meet." 

 So also in endeavouring to explain the motions of eugenic acid (see 

 note 22 ), eddies are formed and an indraw such as are due to the opera- 

 tion of well-known forces apart from surface-tension. 



