252 Mr. C. Tomlinsoii on the Cohesion-Figures of Liquids 



Glass No. 1 . — 1 oz. water. 

 Third drop had not disap- \ ™£ 



peared after J 



When this drop was first placed 

 on the water, it repelled the film, 

 and the crispations set in although 

 sluggishly. No vollies of small glo- 

 bules. The edge like that of win- 

 dow glass. After 1 minute it became 

 still. After 2 minutes lenticular, 

 slowly sailing about, with occasional 

 jerking of the edge. After 7 mi- 

 nutes, slowly revolving on vertical 

 axis. After 13 minutes, slowly sail- 

 ing about. After 25 minutes, a very 

 convex lenticule. After 60 minutes, 

 at rest and slowly evaporating. 



In connexion with creosote, 

 acid is interesting. (See Plate.) 



Glass No. 2. — 2 ozs. water. 



Third drop disappeared in 1 "'r^' 



about J 



The disc active and vigorous, and 

 of good figure, with vollies of mi- 

 nute globules. After 20 minutes, 

 broke up into three portions, two of 

 which were active ; then one split 

 into three or four, which were scat- 

 tered to a distance ; then all still : 

 crispations slowly resumed, and after 

 25 minutes only a few globules, 

 scarcely visible, remained. 

 Fourth drop had not disap- \ , , ~ 



peared after J 



The drop was active for a few 

 minutes, then subsided into a well- 

 shaped lenticule, which slowly dis- 

 appeared by evaporation. 



the cohesion-figure of carbolic 

 It is an exaggerated form of the 



figure of creosote; the water seems to tear it to pieces; the cris- 

 pations are amazingly active, and the disc quickly breaks up and 

 disappears. Indeed, while a drop of creosote will endure five 

 minutes in an ounce of distilled water, a drop of carbolic acid 

 will last only a few seconds in the same quantity of water. The 

 cohesion-figure is, however, quite characteristic of the substance, 

 and cannot be for a moment mistaken for any other substance 

 that I have examined. • 



In cases of this kind, where the conditions are different, we 

 get different cohesion-figures. It has already been stated that, 

 by changing the receiving surface, as by substituting mercury 

 for water, we get a new figure from the same liquid. So, also, if 

 we change the character of the liquid, we vary the figure. The 

 figure given by the unwashed sulphuric ether of the shops is very 

 different from that afforded by rectified ether. Let us take up a 

 quantity of the former in a dropping tube, and gently deliver it, 

 drop by drop, to the surface of about 2 ozs. of water in a clean 

 foot-glass. The very act of gently placing a drop of ether on 

 water leads to the formation of a disc of condensed vapour, just 

 as in pouring ether from a bottle we must first pour a quantity 

 of vapour. As the drop of ether is hanging over the water, it 

 forms a well-defined circular disc or film of condensed ether- 

 vapour on the surface of the water immediately below the drop 

 of ether. But as soon as the drop is delivered to the water, it 

 combines with this disc, and spreads into another disc to the 

 utmost limit of its cohesion : it forms, in fact, a circular or cen- 

 trifugal wave of such extent that there is not matter enough to 

 prevent the centre from opening and following the general im- 



