ill be the greatest of all."(10)

This was only one of several interesting and important communications
sent to the Royal Society during his lifetime. One of these was a report
on what he calls "Pneumatical Experiments." "Upon including in a vacuum
an insect resembling a beetle, but somewhat larger," he says, "when it
seemed to be dead, the air was readmitted, and soon after it revived;
putting it again in the vacuum, and leaving it for an hour, after which
the air was readmitted, it was observed that the insect required a
longer time to recover; including it the third time for two days, after
which the air was admitted, it was ten hours before it began to stir;
but, putting it in a fourth time, for eight days, it never afterwards
recovered.... Several birds, rats, mice, rabbits, and cats were killed
in a vacuum, but if the air was admitted before the engine was quite
exhausted some of them would recover; yet none revived that had been
in a perfect vacuum.... Upon putting the weight of eighteen grains of
powder with a gauge into a receiver that held several pounds of water,
and firing the powder, it raised the mercury an inch and a half; from
which it appears that there is one-fifth of air in gunpowder, upon the
supposition that air is about one thousand times lighter than water; for
in this experiment the mercury rose to the eighteenth part of the height
at which the air commonly sustains it, and consequently the weight of
eighteen grains of powder yielded air enough to fill the eighteenth part
of a receiver that contained seven pounds of water; now this eighteenth
part contains forty-nine drachms of water; wherefore the air, that takes
up an equal space, being a thousand times lighter, weighs one-thousandth
part of forty-nine drachms, which is more than three grains and a half;
it follows, therefore, that the weight of eighteen grains of powder
contains more than three and a half of air, which is about one-fifth of
eighteen grains...."

From 1665 to 1681, accepting the tempting offer made him through
Colbert, by Louis XIV., Huygens pursued his studies at the Bibliotheque
du Roi as a resident of France. Here he published his Horologium
Oscillatorium, dedicated to the king, containing, among other things,
his solution of the problem of the "centre of oscillation." This in
itself was an important step in the history of mechanics. Assuming as
true that the centre of gravity of any number of interdependent bodies
cannot