leticeen some Kinds of Fluids, 157 



out a drop of oil, expels it, assuming its place, and oblisfct! 

 it to concentrate itself. In like manner, if a little cotton 

 dipped ill spirit of wine, or a drop of that fluid, be applied 

 to the surface of water on which float small bits of gold or 

 silver leaf, they are seen to recede. These small bodies re- 

 cede also sometimes from the surface of the water where 

 they are placed, on the approach of a small bit of cotton 

 well dipped in spirit of wine : but they do so faintly, and 

 not with that velocity as when a little cotton dipped in 

 ether* is applied; because spirit of wine, both in the fluid 

 state and state of vapour, on being applied to the surface, of 

 the water, has the property of diffusing itself over it like 

 oitv substances. 



But if a drop of the milky juice of the tithymalus be 

 previously applied to the surface of the water, and if small 

 bits of gold or silver leaf be thrown over it, and if it be 

 then touched as usual with a little cotton dipped in spirit of 

 wine, or if a drop or two of the same fluid be poured over 

 it, the supernatant small bits of metal will not be seen to 

 exhibit the same pha;nomena as before, because the spirit of 

 wine traverses the surface of the water occupied bv another 

 ■fluid, v;hieh has a greater attraction for it. The case is the 

 same when there is applied to the surface of the water any 

 fluid exceedingly volatile and oi!\-, when it has been pre- 

 occupied by the juice of the tithymalus ; but this juice, as 

 soon as it touches the surface of the water f, expels from it 

 all the oils most volatile, and the most odoriferous, and 

 obliges them to concenirate themselves at the cxlremiiies of 

 the vessel under the form of small globules. 



If these repidsions are occasioned by theim]ictuous efflux 

 of volatile and odoriferous einanations, why has the milkv 

 juice of the tithymalus, which is neither volatile nor odori- 

 ferous, the faculty of expelling from the surface of water 

 the most volatile and nl0^t odoriferous fluids ? However, 

 if a drop of spirit of wine be placed gently in the middle oi 

 a dish, and the vessel be then moistened with water in such 

 a manner that the water shall approach only within the 

 distance of two lines of the said drop, it will be seen, belbre 

 it dilates, to exercise a repulsion on the water which sur- 

 rounds it, chiefly when it approaches near tu it ; and, in 

 mv opinion, this effect is owing to the vapours of the spirit 

 ot'wine, which act at a distance; not because the water is 



• See my answers to Prevost, in which it is seen that ctl-t! i^ a lluij 

 which appro iches nearer than spirit of wine to the nature or" oiU. 



f Mriniilr on Actrviciio'i of Surface, in vo!. xi. of tht- TKiiisiirtions f-.f 

 the Italian Boi icty 'if the SlIct.cc}. 



evpi Hod 



