270 PHILOSOPHICAL TRANSACTIONS. [aNNO 1675-6^, 



shall need to add, for the removal of this subtle scruple no more, than this plain 

 experiment, (which I twice or thrice made,) namely, that taking instead of a 

 calx of gold, a competent number of leaves of gold, such as book-binders and 

 the apothecaries use, this gold that was without the help of salts reduced by- 

 beating to a sufficient thinness (insomuch that 70 odd leaves did not weigh a 

 scruple,) I found (more than once) upon putting two or three times the weight 

 of our mercury to them, that a smart heat was presently produced in my hand. 



Observations on several Passages in the last tivo Months Transactions, relating to 

 some unobserved Qualities of tlw Air ; to the Mixing and Fermenting of Liquors 

 in vacuo ; to the History of Birds ; the Anatomy of the Trunks of Vegetables ; 

 Baroscopes, &c. N° 122, p. 533. Anonymous. 



Corrosions of bodies, especially with a sensible motion, by emitting effluvia, 

 which may also be springy themselves, if saline, may further bend the springy 

 particles of the air, giving it a greater elasticity. On the contrary, other cor- 

 rosions not so emitting, by different ways, may weaken this spring. 



In the first experiment, (in a late paper by Mr. Boyle) the solution may ac- 

 quire a brown colour by the menstruum's imbibing the particles of copper into 

 itself, which would alter its texture ; and the impeding particles, diversifying 

 the refractions and reflections, may modify the rays of light ; or, as it is in 

 Mr. Newton's theory, the solution may be qualified only to admit such rays 

 whose degrees of refrangibility, and mixture with other rays, may be predis- 

 posed to give a brown, to which effect the air did much contribute. 



So perhaps in the second experiment the delay of regaining was to be im- 

 puted to the cold or moisture, or other critical circumstances of the air, having 

 less of those dissolving particles which make it a menstruum on those bodies. 



Those ingenious Frenchmen, excited by Mr. Boyle, the glory of learning, 

 as well as of our nation, having given us an attempt of mixing and fermenting 

 liquors in vacuo, do prosecute fermentation, particularly of that in the growth 

 of plants; how it may be impeded or promoted by the absence or presence of the 

 air. 



In the continuation of January, by which and what Mr. Boyle has written, 

 we see the nature of the air, its effects on bodies when present ; by procuring 

 its absence. Now Sir W. Petty can no more complain at the idle employment 

 of weighing air; for the doctrine being well illustrated, and the theory esta- 

 blished, we thus descend again to more useful and grounded experiments ; as 

 the method mentioned by my Lord Bacon, to proceed from experiments to 

 axioms and assertions; from these, as too general, to particular and useful ex- 

 periments, which before we could not do, till we had cleared the doctrine from 

 wide and extravagant guesses. , 



