aiake Barofcoptcal Obfervations in feveral parts of England (if 
* „ . not in forrain Countries *'a!fo 5 V 
; *"* and to affift them, to do fo, -prefen- 
« concurrence herein. <* d fome of Frlends with the 
neceffary Inftruments : The decla- 
red reafon of my de firing- this Correfpondence was f among 
other things) that by comparing Notes , the Extent of the At- 
mofpherical Chances , in point of Weight, might be the better esti- 
mated, But not having hitherto received fome account, 
that I hoped for, I fliali now, without ftaying for them, intimate 
thus much to you : That it will be very convenient: , that the 
Obfervers take notice not only of the day 5 but, as near as they 
can , of the Howe wherein the height of the Mercurial Cylinder 
is obferv’d: For I have often found, that within lefs than the 
eompafs of one day, or perhaps half a day, the Altitude of it 
has fo confiderably vary *d, as to make it in many cafes difficult, 
to conclude a n y t h i n g ee r t a ip ly fr o m O b fer va tic n % ; tha t agree 
%ut in the day. 
It will be requifite affo, that the Obfervers give notiefe of 
the Scituation of the place , where their Barometers ftand, not 
only, beeaufe it will affift men to Judge, whether the Inftru- 
ments were, duely perfected, but principally , beeaufe, that 
though the Barofcope be good ( nay, beeaufe it is fo ) the Ob- 
fervations will much difagree, even when the Atmofphere i$ 
in the fame ftate , as to Weight, if one of the Inftruments 
ftand in a confiderably higher part ©f the Countrey* than the 
other. 
To confirm both the foregoing admonitions, I rnoft now in- 
fer® you. that 5 having in thefe parts two Lodgings, the one at 
‘Oxford, which you know ftands-in a bottom by the Thames fide 3 
and the other at a place.four miles thence, feated upon a mode* 
pa tQ Hitt, I' Found,’ by comparing two Barofcopes, that I made., 
th:e one at Oxford \ the other at Stanton $ tt Johns , that 5 though the 
former be very good; and have been noted for fuch, during 
fome years, and the latter was very- carefully fill’d ; yet by 
seafcii, that in the Higher- place, the incumbent part of the At- 
mofphsie mu it be lighten, than in- the Bower % there is glraoft al- 
ways. , 
