C 5*7 ] 
LXXXVIII. A Letter of Mr . James Short, 
F. R. S. to the Royal Society, concerning 
the Inventor of the Contrivance in the Pen - 
dulu?n of a Clock , to prevent the Irregula- 
rities of its Motion by Heat and Cold > 
Gentlemen, 
Read^Nov. g, fubjedt of converfation of late 
I having often turn'd upon that in- 
genious contrivance in the pendulum of a clock, to 
prevent the inequalities in its motion, ariflng from its 
different lengths, in different feafons of the year, by 
the effects of heat and cold ; and it having been often 
afked, who was the inventor of it, I have therefore 
thought proper to draw up the following hiftorical 
account of it : And as this account contains nothing 
but matters of fadt, fupported by the belt authorities, 
I hope it will be acceptable to this Society. I am 
Your mofl obedient humble fervant, 
J. Short, 
S OON after the invention of pendulum-clocks 
(juftly aferibed to the celebrated Mr. Huygens), 
it was found, that they were liable to confiderable 
inequalities in their motion ; which were imagined 
to arife from the pendulum, in its vibrations, de- 
scribing an arc of a circle ; and, confequently, that 
the larger vibrations muft be flower than the fhorter 
ones. 
