1()2 PHILOSOPHICAL TRANSACTIONS. [aNNO 1685. 



red liquor will rest as quietly as any ordinary one, without sending up any 

 smoke. But if the phial be unstopped, so that the external air be admitted, in 

 a quarter of a minute, or less, there will be elevated a copious white smoke, 

 which will not only fill the upper part of the glass, but be plentifully discharged 

 into the open air, till the phial be again stopped. And a little after he adds, 

 if the unstopped phial were placed in our vacuum, it would not emit any visible 

 steams at all, nor so much as appear in the upper part of the glass itself that 

 held the liquor; whereas, on gradually restoring the air, the returning air 

 would presently raise the fumes, first into the vacant part of the phial, whence 

 they would ascend into the capacity of the receiver ; and likewise when the air 

 was pumped out, they also accompanied it, and the red spirit, though it re- 

 mained unstopped, emitted no more fumes, till the new air was let in again : so 

 far Mr. Boyle. Such then was the proportion between the gravity of the 

 vapours of this red liquor and the air, that the air being in its ordinary degree 

 of gravity, these vapours did ascend ; but the air's gravity being much lessened 

 in the receiver, by the pumping out a great deal of it, and so expanding the 

 springs of the rest, it was incapable to elevate those vapours. 



A Discourse concerning the Airs Gravity, observed in the Barometer, occasioned 

 by that of Dr. Garden ; presented to the Phil. Society of Oxford. By the Rev. 

 Dr. fVallis, President of that Society. April 14, l685. N° 171, p. 1002. 



The discourse of Dr. Garden, read at our last meeting, concerning the 

 different state of the air, in respect of its different gravity, has in it a great deal 

 of very ingenious speculation. And what I then said of it, on the first reading, 

 and what I am now saying again to the same purpose, is not to contradict it, or 

 detract from it, but to add to it; as a notion which I have long since considered, 

 and judge it capable of further improvement. 



The notion of the air's weight and spring has been so well settled, by in- 

 numerable experiments, that hardly any considering person now doubts of it. 

 And it has chased away the notion of fuga vacui, formerly received, by showing 

 us an efficient cause of those effects, for which before we could only pretend to 

 a final cause. The first occasion, that we know of, of introducing it, was from 

 Galileo's discovery, that water by pumping, was not to be raised higher than 

 about 3 or 4 and 30 feet of our English measure. Which was a certain argu- 

 ment, that the cause of those effects, commonly ascribed to fuga vacui, was 

 but of a finite strength : whereas, if nature's shunning a vacuity had been the 

 true cause, it was to have operated without limit. Upon this, that Lyncean philo- 

 sopher, as he was called out of his great sagacity, happily guessed at the coun- 

 terbalance of the air's weight, as the true. cause. And that therefore air, which 



