flownes, as to finifh one entire Revolution in 24 hours; 
and while it does fo, the divifions on the horary circle 
(or Dial-plate) lucceffivcly culminating over the point 
of the Index, willfhow the hours of the day and night. 
For in this Movement (contrary to what is ufual in o- 
thersj the hour is difcover'd by the accefs of the num- 
bers to the Index i which (as was faid Par ic. i>) is al- 
ways to keep the fame Pofition. Now. when by feveral re- 
peated Revolutions it has meafur'd out the length of its - 
ftage,it is to be replaced at i'.as before^ which may be done , 
in Jels than half the time you are winding up a Watch; 
and if the ftage be but 6 foot long, no oft'ner then once 
in a whole week. 
4. The way of adjufting this Motion to the exadt mea- 
fure of an hour, and rediifying its errors; comes in the 
laftplacetobe provided for. No Movement could e- ; 
veryet be found, that would keep pace with the Sun; 
and the Reafon of this, befides the alteration of wea- 
ther, and other common accidents to which the mofl 
curious Movements are liable ; is becaufe the Sun it felf . 
does not always keep the fame pace, nor is the precife 
duration of a lolar hour in any one day fo exactly affign- ^ 
able, as to ferve indifferently for the whole Year round. - 
But leaving that jijironomical Enquiry to fuch as have 
better helps and opportunities for Celeftial Obfervations i 
I fhall crave leave to think, that if no greater objection : 
can be rationally made to this Movement, then the ne- 
ceflity of its being fometimes adjufted andrddify'd j e- j 
ven this will appear a very inconfiderable one, lince the ; 
manner of doing it, is fo very obvious and eafie. To 
explain this, 'tis to be confider d that there are two Er- 
rors which every Movement is fubjed: to, and indeed fcarce 
ever entirely free from,tho when the aberration is fo fmall 
as not to be difcernable, it pafles for truth. , The firfl: of 
thefe is, when a Movement gives you a wrong meafure 
of an hour, by going remarkably too fafior too flow ; 
and this is an error in the whole train of the Movement 
from the beginning to the end. The fecond Error iS:, 
when 
