[790] 
A difcourfe concerning the rifing and falling of th 
Quickfilver in t be Bzrometcr ; and what maybe 
gathered from its great rife in Frofty weather, as 
to a healthy orfickly feafon ; prefentedthe Roy- 
al Society Mm/; 2 0. 1 683. by thh Learned Dr. 
Martiia Lifter, Fellow of the K.S. "^'''^ 
"T Do not offer thefe things Dogmatically as though I 
I ^had light upon certain Truths s but only as probable 
^ 'Conjectures, and fuch as may as well account for the 
^Phiemmena of the Barometer^ as any I know. I am of 
opinion , That it is not good, if we intend the Advance- 
mcnt oi Natural Philo/ophyy to let any part of it reft too 
long upon one Bafis; For he that is once well pleafed 
With an Opinion, naturally acquielces, and feeks no fur- 
ther. However admitting the Gravitation of the Jir^ 
I have a mind to try how far I may go in lome additio- 
nal thoughts I have about the Barometer^ though they 
maypoffiblybe much different from what hath hitherto 
teen propofed about it. 
1. It is to be obferved, thgt,t §uickflver is not affed- 
cd with the Weather^ or very rarely, let that be either 
Cloudy, Rainy, Windy, or Serene in St. Helena ; or the 
IRarbadoes : and therefore probably not within the Tro- 
picks, unlels in a violent Storm or Hurricane. The firft 
is afBrmed by Mr. Halley^ who kept a Glafs near two 
Months in the Ifland St /Helena, and the other oi Bar- 
hadoes ftands upon the Credit of our 'Regijlers. 
2. In £;/^/i^w^in a violent Storm, or when the §luicl^ 
filver is at the very loweft, it then vifibly breaks and e- 
mits fmall particles, as I have more then once obferved ; 
which dilorder I look upon as a kind of Fretting 5 and 
cpnlequently at all times in its Defcent, it is more or lefs 
^pon the Fret. 
In this diforder of the ^ckfdver^ I imagine it hath 
its 
