, "for presently
other difficulties concerning it arose. For example, unless the water
poured into it was absolutely clean, the hole would fill up and the drip
become slower; moreover, you must consider what happened in cold
weather, for not only were these water clocks in unheated buildings, but
you will recall they were set up in the market place or public square so
the villagers might consult them. Here assembled the watch, whose duty
it was to patrol the town and blow a horn for the changing of the guard;
here, too, was stationed the officer whose duty it was at stated hours
to refill the clepsydra."

"Oh, I suppose the darn thing froze--that probably was the next
obstacle," grinned Christopher.

"It was," nodded McPhearson.

"Then it couldn't have been much better than the old sundial," the lad
sniffed, with contempt.

"It had its outs. Nevertheless it held the front of the stage about two
thousand years, and then I am sure you will agree it was high time a
better device was substituted."

"And what was that?"

"The sand glass."

"Our hourglass, you mean?"

"Yes--or half-hour, quarter-hour--any fraction of an hour you choose.
The idea of the sand glass was not entirely new, because some form of
running sand had long before been used in the Far East. But the sand
glass as we know it was new to the European world, and you cannot but
agree it was a far more practical article than was the clepsydra for it
neither froze nor had to be replenished. Moreover, it was lighter, less
bulky, and could be carried about, and the old water clocks could
not--that is, not without great inconvenience and danger of breaking.
Oh, the sand glass was vastly better! Even now, after all these years,
it is not entirely out of date, for it is still used to mark definite
intervals of time."

"I have one at home to practice by."

"Many persons use them," the clockmaker averred. "It is not unusual to
have speakers limit their addresses by them. In fact, a two-minute glass
is still employed in the House of Commons and until 1839 the British
Navy measured the watch on shipboard by a glass that ran an hour and a
half. The marking off of time in such definite lengths as this, however,
did not take place in ancient times. At that period people seldom
attempted fine measurements of the day. The problem of hours, minutes,
seconds, and fractions of them was something they scarcely dreamed of.
Nor did they need to cut their time up into su