458 NATURAL HISTORY. 



was in India a kind of brass, which, being polished, 

 could scarce be discerned from gold. This was in 

 the natural ure : but I am doubtful, whether men 

 have sufficiently refined metals, which we count base ; 

 as whether iron, brass, and tin be refined to the 

 height ? But when they come to such a fineness, as 

 serveth the ordinary use, they try no farther. 



Experiment solitary touching cements and quarries. 



850. There have been found certain cements un 

 der earth that are very soft ; and yet, taken forth 

 into the sun, harden as hard as marble : there are 

 also ordinary quarries in Somersetshire, which in the 

 quarry cut soft to any bigness, and in the building 

 prove firm and hard. 



Experiment solitary touching the altering of the colour 

 of hairs a nd feath ers. 



851. Living creatures generally do change their 

 hair with age, turning to be grey and white : as is 

 seen in men, though some earlier, some later ; in 

 horses that are dappled, and turn white ; in old squir 

 rels that turn grisly ; and many others. So do some 

 birds ; as cygnets from the grey turn white ; hawks 

 from brown turn more white. And some birds there 

 be that upon their moulting do turn colour ; as robin- 

 red-breasts, after their moulting, grow to be red 

 again by degrees, so do goldfinches upon the head. 

 The cause is, for that moisture doth chiefly colour 

 hair and feathers, and dryness turneth them grey and 

 white : now hair in age waxeth drier ; so do feathers. 



