484 PHILOSOPHICAL TRANSACTIONS. [anNOIVOQ. 



I mixed also some common water with a strong purple liquor, made from log- 

 wood boiled in water, in which some alum had been dissolved. A little of this 

 would give a strong tincture to a considerable quantity of fair water ; and when 

 exposed to freeze, would retire towards the middle leaving the first frozen water 

 of a very pale purple, in comparison of the middle part ; which when I had 

 taken out of the glass that contained it, and broken it, I found it was frozen 

 through, but of so dark a colour in the middle, that it came near a black. 



An Experiment of fVeighing in Common JVater, Bodies of the same Species, 

 and of an equal weight in Common Air, but of very unequal Surfaces. By 

 Mr. Fr. Hauksbee, F. R. S. N° 320, p. 306. 



I took an exact square inch of sheet-brass, weighing just 482 grains : I then 

 cut as many square inches of brass tinsel, as were equal to the same weight ;• 

 the number of these square inches being 255. Now these being of an equal 

 weight with the other single piece in common air, I concluded from the ine- 

 quality of their surfaces, that a considerable disproportion in their specific 

 gravities would ensue, by weighing them in water ; the water in one touching 

 so many parts of the superficies more than in the other:* and from what is 

 generally asserted, that the smaller the bodies are, so the disproportion of 

 their bulks to their superficies increases ; and that supposing them infinitely 

 small, or as gold dissolved in aqua regia, or silver in aquafortis, that then their 

 superficies being touched by so many parts by the including menstruum, which 

 is in such a disproportion to their diameters or bulks of matter, as disposes 

 them to remain suspended in it. This I take to be the general solution of that 

 phenomenon. Yet when I came to bring it to the test, I was surprised to find 

 only 2 grains diflference, the single piece weighing in the water about 422 

 grains ; and all the other bodies together, scarcely 2 grains less. And this upon 



* The language employed in this paper shows an extraordinary instance of the vague and con- 

 fused notions of the writer on some physical properties: and it is truly surprising that Mr. Hauksbee, 

 who invented and executed so many curious experiments, who had the benefit of ingenious authors 

 on hydrostatics, &c. and who enjoyed the advantage of the ideas and conversations of the learned 

 philosophers of his day, should be ignorant of the nature of the specific gravity of bodies, and the 

 ■manner of determining it. He seems to think it depends partly on the surface of the body, as well 

 as on its bulk or magnitude, instead of the latter only, under the proportional weight. So that, 

 according to him, the half of any body should not have the same specific gravity as the whole of it. 

 His notions also on the support of bodies in fluids seem very crude and incorrect : bodies when re- 

 duced to very small parts, as to powder or dust, having such parts often tustained in fluids, not from 

 a change in their specific gravity, but from the viscidity or the cohesion of the parts of the fluid, 

 which the small weight of the particles of the body, in proportion to their surface, is not able to 

 svcrcome, and force themselves through. 



