[ S 2 ° ] 
a particular fort of pallets, fo as to be aim oft intirely 
free from friction ; for tho’ he had thus happily fuc- 
c.eeded in his contrivance to prevent the inequalities 
in the motion of the clock, arifing from the different 
lengths of the pendulum by the effects of heat and 
cold, yet he found there were confiderable errors 
{till remaining, occafion’d by the fridtion of the pal- 
lets, as in the common way. He has alfo fufpended 
the pendulum upon the wall of the houfe, intirely 
independent of the clock and clock-cafe: For he had 
obferved confiderable alterations in the going of the 
clock, when the pendulum is fufpended as in the 
common manner. His pendulum vibrates in an arc 
of about i y degrees, with a bob t>f about three 
pounds, between cycloidal checks, which he him- 
lelf found were neceffary, tho’ he had never heard 
of M. Huygens’s book, till after he had made them. 
He has alfo difpofed the force of his pendulum-wheel 
upon the pendulum, by his fort of pallets, in fuch 
a manner, that the vibrations of the pendulum will 
not be affedted by the different refinance of the air. 
Upon the whole, this clock is made in fuch a man- 
ner, as to be almofl intirely free from fridlion ; in 
confequence of which he ufes no oil, and therefore 
there is no neceffity ever to clean the clock. When 
he fettled in London, he fent for one of thefe clocks 
from the country, and fet k up in his hcufe in Orange- 
flreet, in the year 1739, where it has flood ever fince, 
and in all that time has never varied above one minute 
from the truth. He can -depend upon it to afecond 
in a month. 
About the year 1729, Mr. Harrifon made his fir ft 
machine for meafuring time at fea, in which he has 
likewife 
