M. Van Swindon on the Invention Pendulum-Clocks 
tions,” But as the same assistant has to count the number of 
oscillations which it performs, he proposes, as a tolerably easy 
mode of avoiding this troublesome labour, (un assai commodo 
provredimento^) that from the middle of the vibrating sector 
there should project a pin, which^ when the pendulum swings 
to one side, should meet the upright part of a tooth belonging 
to a small crown-wheel, as light as paper, {leggierissima quanto 
una carta^) and impel it round its axis, but on swinging back- 
wards, ascend along the sloping side of the same tooth, and 
leave the wheel unmoved ; so that one tooth might be impelled 
at each entire vibration, and the number of vibrations be shewn 
by the revolution of the wheel, which might likewise be con- 
nected with a larger wheel by means of a pinion.” But,” he 
adds, it is unnecessary to explain all this to you, who possess 
choice arid practised artists in the construction of clocks and 
other machines; because those people, on learning the new 
principle, that a pendulum performs its oscillations in very equal 
times, whether it describes larger or smaller arches, will be able 
to draw from it much more subtile consequences than I can 
imagine.” From this it appears doubtful, whether Galileo ever 
himself tried the contrivance of the pin and wheel, and did not 
rather throw it out as a hint for others to improve upon, than 
as the result of actual experience. He then concludes in these 
remarkable words : “ In these very simple pendulums, then, 
which are subject to no alteration whatever, (alter azione alcune^ 
is contained the method to preserve in an easy manner a con- 
stant measure of time : and you will perceive their utility and 
the advantages they possess in astronomical observations, which 
do not require that the oruolo should always go, but where it 
is sufficient to know from the hours of noon, or of the setting of 
the sun, the smaller divisions of time, for an eclipse, conjunction, 
or other celestial phenomenon.” 
These extracts need no comment. They prove abundantly 
that the word oruolo^ though used long before that period, to 
express a clock moved by wheels and weights, was the name 
adopted by Galileo to designate this loose pendulum, the invent 
tion of which, as the measure of time, belongs undoubtedly to 
him. That it continued to be called by that name for some years 
after, is manifest from a French work, printed at Paris ill 1639^? 
