( t779 y 
Air, Of wBen the Receiver was put over the little Move- 
ment, (but unexbaufted^ ) yet when the Receiver was ex- 
haufted, tlie HeiU-feconds Movement would lofe, at the 
rate of two ieconds In every hour, in every Experiment, in 
many, hours going, 
And^ becaule I was minded to fee what alterations, 
%ould arife from: varying the Vibrations, therefore by 
■opening and (hutting the Pallets, I caufed the Vibrations 
in fome Experiments to be as large as the Receiver would 
bear ^ in, others, to be as (hort as poffible ^ always adjaft-^ 
ing the Pendulum to vibrate Half feconds- nicely in the 
Air. But ftill the fuccefs was much the fame, or the dif- 
ference fcarce perceptible. But only I imagined when the 
Pendulum vibrarcd but a little way from the Perpendicu- 
lar, thart the Vibrations i^i Vacm wctq not fo much en- 
larged, as when it vibrated in a larger Arch. 
In all rhefe Experiments ( which were repeated divers 
times with the fame fuecefs ) i had no reafon to move me 
to think, -but that the Vibrations were enlarged m Vacm 
by the vaft Rarefadion of the Medip,m -: I had I fay 
reafon but this, That perhaps the different ftate of the Air 
Height alter the force of the Spring, which drove tiie 
Movement. For the tryalof this, I put a well adjafted 
Pocket-V/aich ( with H/?t>^ s FvCgulator, I e. the common 
fmall Spiral Spring -to the Ballance ) into th^ Vacmwu 
And after feveral tryals, at the farne pitch of the Spring, I 
found not the leaft alteration in the Watches going in 
many hours ^ neither the Springs, nor any other part of 
the Watch fecroing to be in the leaft affefted by th^ Va^ 
€Mum : but the Baiiance circumvoiving, or keeping the 
fame Turns, as in the open Air. ' 
" But to be ftill more fure, if poffible ^ it came after this 
into my thoughts, to try what the fuccefs would be by 
putting the Half' feconds Pendulum again intothe Receiver, 
and only ppthpirig out a part of the Air. And accordingly 
I left no more Air in', than what kept the included MercuriaL 
,Gauge 
