WEIGHT IN AIR AND WATER. 411 



an egg turned into stone, the white and the yolk keep- 

 ing their colour, and the shell glistering like a stone cut 

 with corners. 



Try some things put into the bottom of a well ; as 

 wood, or some soft substance : but let it not touch the 

 water, because it may not putrify. 



They speak, that the white of an egg with lying 

 ong in the sun, will turn stone. 



Mud in water turns into shells of fishes, as in horse- 

 mussels, in fresh ponds, old and overgrown. And the 

 substance is a wondrous fine substance, light and shin- 

 ing. 



CERTAIN EXPERIMENTS MADE BY THE LORD BACON 

 ABOUT WEIGHT IN AIR AND WATER. 1 



A NEW sovereign of equal weight in the air to the 

 piece in brass, overweigheth in the water nine grains : 



1 Baconians, p. 134. 



Bacon derived this method of weighing in air and water from Porta, who 

 in his Natural Magic speaks of it as so great a thing as to entitle him to say 

 i'TrepEvprjua vnepevprjKa referring of course to the story of Archimedes. 

 Of course it is possible to calculate specific gravities from experiments in 

 which both scales of the balance are immersed in water; but Porta's rule 

 for determining the amount of alloy contained in a piece of gold is alto- 

 gether wrong, and how confused his notions were is shown by his directing 

 the experimenter to immerse the scales circiter semipedem, as if the depth 

 made any difference. So too Bacon speaks of immersing one of the scales 

 five inches. Porta, a little further on, records some experiments made by 

 immersing only one of the scales; and so we may observe does Bacon, a 

 circumstance which makes it plain that he was following Porta's directions. 

 The notion of weighing in air and water was however not new. It is 

 treated of at some length by Nicholas De Cusa. But Cusa's notions are 

 at least as confused as Porta's. Thus he wants to determine not only the 

 pondus yravitatis, but other kinds of pondera ; and remarking that lead 

 comes next to gold in pondus graritatis so that it would seem as if the 

 comparative value of metals could not be determined by the balance goes 

 on to say that if we take account of the pondus ignis, then silver would, as 



