6lO PHILOSOPHICAL TRANSACTIONS. [aNNO 1701. 



gummy and unctuous matter; for it is very light, swimming on brandy and oil, 

 and not uniting either with water or spirit of wine, or any other liquor, except 

 oil alone; and besides it burns or takes fire, for I have dipped cotton in it, which 

 has burned all away to ashes, though at first there was some difficulty to make 

 it take fire; owing perhaps to some other matter not unctuous being mixed with 

 it. And lastly, since, being observed with the microscope, its composition 

 shows like that of oil or lard, or the like unctuous matter, it is very probable 

 from all these, that it is composed of the gum or juice of some resinous herb or 

 tree, or of the fat of some animal, or hog's lard. And, to make some guess, 

 possibly the gall of fome animal may be mixed with it, to make it the more 

 easily receive a smoothness and lustre, as limners use to put gall into their 

 water-colours, to make them run and spread the better ; and that the mischief, 

 found by touching and using it, may proceed from hence. 



I believe there is no mercury in this varnish; not only because it is very light, 

 but because I have been very diligent in trying whether gold would discover any 

 sign of mercury, either in the body of it or the smoke, but could never find 

 any ; and besides, mercury produces very different effects in our bodies from 

 those of this varnish. 



I have observed that the varnish mixed with spirit of vitriol, juice of lemons, 

 or vinegar, or spirit of wine, makes no ebullition, nor change of colour; but 

 it readily changes colour, when taken out of the vessel and exposed to the air, 

 becoming at first reddish, and afterwards almost quite black ; the outward skin 

 of it, which is next to the air, becoming very hard and black ; this skin is very 

 thin, under which the rest of the varnish remains soft and fluid, of the colour 

 and consistence of honey; and as often as you take off this outward black hard 

 skin, there will be formed immediately another like the former, and this as 

 often as you please to repeat the experiment. So that the whole substance of 

 the varnish will in time be changed into these hard and black skins. 



Finally, it is worth observing, that this varnish has this known power ; for 

 having spread some of it on the naked breast of some fowls, leaving it sticking 

 there for three days. I afterwards found between the dried varnish and the flesh 

 the place all festered, and full of a yellowish serum, but without any further 

 harm. I have attempted the same thing in dogs and cats, but without success, 

 for these animals with their tongues and claws soon take off all the varnish from 

 their bodies, and so take no hurt by it. Possibly in horses, and such like ani- 

 mals, the experiment might succeed better if the varnish has this corrosive or 

 caustic quality on their bodies that it has on poultry. 



