VOL. XI.] PHILOSOPHICAL TRANSACTIONS. ' 363 



cavity, which in a great breadth would seem less deep, might be the more con- 

 spicuous; we gently poured on it some highly dephlegmed spirit of wine, whiph 

 we knew would not mix with it, but swim above it, land presently we found the 

 figure of the surface of the lower liquor changed, and the cavity quite de- 

 stroyed; the surface that seemed, as it were, common to the two contiguous 

 liquors, appearing flat or horizontal. And such a level superficies we had by 

 putting those two liquors together in a much wider glass. 



We found also, that by employing oil of turpentine instead of spirit of wine, 

 the liquor almost totally lost its cavity. But if, instead of deliquated tartar, we 

 put common water into the pipe, we found this liquor to retain its concave 

 surface, though we put to it some oil of turpentine, and left it to rest on the 

 water a good while. Having provided some pure oil of gum guaiacum, which 

 is heavier than water, and poured a little of it into a slender tube, the upper 

 superficies of it became concave; almost, if not altogether, like that which 

 water would have had in the same place. But when I put a little water upon 

 this oil it presently changed the figure of its surface, which became visibly, 

 though not very much, protuberant or convex. 



And as this oil, though heavier than water, is not so heavy as deliquated salt 

 of tartar, I thought fit to try, whether the phenomenon would not be diff'erent 

 upoii the contact of those two liquors; and accordingly having put some oil of 

 tartar into the slender pipe, and some drops of the oil of guaiacum to it, this 

 liquor did not manifestly alter the concave figure of the surface of the liquor 

 alcali, as the oil of turpentine had done; and having warily poured a little water 

 on the oil of guaiacum, the upper superficies of it changed presently from a 

 concave figure to a convex; so that this oil, in the midst of the other two li- 

 quors, appeared like a little red cylinder, which, instead of having circular 

 bases, was protuberant at both ends, but more at that which touched the oil of 

 tartar. 



To vary a little the experiment, I put some essential oil of cloves into a new 

 slender pipe, and having observed it to be somewhat concave at the top where 

 it was contiguous to the air, we caused a little common water, perhaps a quarter 

 of a spoonful or less, to be put to it, and found the surface of this oil also to 

 become tumid. And since this liquor, as well as the forementioned oil of guai- 

 acum, though it were so heavy as to sink in water, would not do so in deli- 

 quated salt of tartar, we put into another slender pipe first some of this last 

 named liquor, then some of the aromatic oil, and lastly a little common water; 

 by which means we found, that the little cylinder of oil did, like that of the 

 oil of guaiacum, appear convex at both ends; but was unlike it in one circum- 

 stance, that the oil of cloves appeared more convex at the upper end, where it 



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