MOTIONS OF FLUIDS. 203 



by an analogous procefs. I coloured alcohol by means of 

 turnfole j with this lubliance it takes a ver^ beautiful colour 

 which is not at ail fimilar to the violet blue of tindure of turn- 

 fole, but, on the contrary, is of a very vivid blue, analogous 

 to that of indigo, or pruliian blue. I then wetted the bottom 

 of a plate with pure water, and, with a glafs rod, brought 

 a drop of this coloured alcohol to the centre: the water was 

 driven back with vivacity. In the centre of the dilk of dif- 

 perfion was a blue fpot, formed by the coloured alcohol, and 

 the reft of the dilk was white like the bottom ot the plate. 

 But the proof of the adual continual emiflion of the coloured 

 alcoholic particles, is that as the water retired, its internal 

 edge, which touched the difk of dilperfion, became more and 

 more of a violet colour, analogous to that of tincture of turn- 

 fole prepared with water. It is evident, therefore that in 

 natural philofophy, fads are explained by fads, and, that this 

 experiment confirms the confequence I had deduced from the 

 preceding experiment. 



8. If the plate is wetted with the alcohol, and a drop of Water does not 

 water is put into the centre, the alcohol does not experience "^^^^ aco o. 

 any motion ; the drop of water flattens, it retains its orbicular 



form for fome moments, at length it finiflies b) fpreading 

 irregularly, mixing with the alcohol, and uniting with it. 



9. If the bottom of the plate is covered with a very thin Oil Is repelled 

 flratum of olive oil, and a drop of alcohol is brought to the "'"''" ^"^'^ ^^^« 

 centre, the oil is repelled, though more flowly tiian the water 



on account of its vilcoiity, and the bottom of the plate is left 

 dry. 



If the ftratum of oil is too thick, it will not quit the bottom 

 of the plate, and the expanfive motion of the alcohol takes 

 place only on the fuperhces of the oil. 



10. If a morlel of the freth rind of lemon or orange is The effential oil 

 placed in the centre of a wetted plate, (he water is fentibly °^ '^'""" °^ 

 repelled, and the difk of difpeifion is agreeably tinged with ducts repuliion, 

 the prifmatic colours, which depends on the dilengagement of ''"^ weaker, 

 the elfential oil. But this motion has not nearly (o much in- 



tenfity as that produced by means of alcohol. 



11. Convinced by the preceding experiments that every The affinity of 

 volatile fluid at the atniofpheric nrefi'ure, wa^ capable of pro- arnmoma tor 



,. , ,^ T 1 .i-i . water prevented 



(lucing this repuluve movement, 1 employea lic[uid ammonia, its repuifuc 



I therefore wetted the pJaie in the ufual manner, and brought action, 



a drop 



