fo much heavier, thaa the Air of the former place was, when 
rhe Mercury ftood at 292 inches. 
But in making fuch companions, we muft not forget to con- 
ifider the Situation of the leveral places, if we mean to make 
Eftitnates not only of the weight of the Atmofphere but o , 
weight anddenfity of the Air. For, though the Scales wil fhewfas 
has been faid ) whether there be a difference of weight m the 
Atmofphere at the two places ; yet, lfotieof them bema /ale 
or bottom, and the other on the top or fomo elevated part of a 
Hill it is not to be exfpe< 2 ed, that the Atmofphere, in this 
latter place, (hould gravitate as muchfas the Atmofphere m the 
former, on which a longer Pillar of Air does lean or weigh. 
And the mention, I have made of the differing Sitnai ion 
Places, puts me in mindoffomething^that may prove a- 
mther ufe of our Statical Barofcope, and which 1 had thought 
jf making tryal off, but was Accidentally hindred front the op- 
portunity ofLing it. Namely, that by exactly poyfmg the 
Subic atthe foot of a high Steeple or Hill, and carrot n 
ts dole Frame to the top, one may, by the weight re ^ U1 ^ 
3e added to Counterpoife there to bring the Beam to it H - 
tontal pofition, obferve the difference of * e ±h 
it the bottom, and at the top 5 and, in cale thejtiiU be mg 
•noush at feme intermediate Stations. But how far this may 
1 (Eft men, to eftimate the Ai folate or Comparative height o 
lou^ins, and other elevated Places; and what other Ufe 
he Ihftrument may be put to, when it is duly improved , a 
he Cautions, thatmayberequifite in the fever.al cafes, 1 
[hall be propofed, I muft leave to more leafure, and farmer 
Confideration. 
The Particulars. 
)fthofe Obfervations of the Planet Mars, formerly intimated 
to have been made at London in the Months ./February 
and March A. t66l. 
To-perform, what.was promifed hum. i i. °f thefe P 
t n i9 8 ; tis thought fit now to pobltfh the Particular • 
%'s concerning the foots in Mars, and their motion^ 
ley were made with a U foot Telefcope , an P ro Siting 
