ntly into the
water, in the posture represented in the first _Figure_, to the bottom,
where the weight D touching first, is thereby stopt; but the Ball, being by
the _Impetus_, it acquired in descending, carried downwards a little after
the weight is stopt, suffers the springing wire to fly back, and thereby
sets it self at liberty to reascend. And, by observing the time of the
Ball's stay under water (which may be done by a Watch, having minuts and
seconds, or by a good Minut-glass, or best of all, by a Pendulum vibrating
seconds) you will by this way, with the help of some _Tables_, come to know
any depth of the sea.

Note, that care must be had of proportioning the weight and shape of the
Lead, to the bulk, weight, and figure of the Globe, after such a manner, as
upon experience shall be found most convenient.

In some of the Tryals already made with this Instrument, the Globe being of
Maple-wood, well covered with Pitch to hinder soaking in, was 5-13/16
inches in diameter, and weighed 21/2 pounds: the Lead of 41/2 pounds weight,
was of a _Conical_ figure, 11. inches long, with the sharper end downwards,
1-9/16 inches at the top, and 1/16 at the bottom in diameter. And in those
Experiments, made in the _Thames_, in the depth of 19. foot water, there
passed between the Immersion and Emersion of the Globe, 6. seconds of an
hour; and in the depth of 10. foot water, there passed 31/2 seconds or
thereabout: From many of which kind of Experiments it will likely not be
hard to finde {149} out a method to calculate, what depth is to be
concluded from any other time of the like Globes stay under water.

[Illustration]

In the same Tryals, made with this Instrument in the said River of
_Thames_, it has been found, that there is no difference in time, between
the submersions of the Ball at the greatest depth, when it rose two
Wherries length from the place where it was let fall (being carried by the
Current of the _Tide_) and when it rose within a yard or so of the same
place where it was let down.

The _other_ Instrument, for Fetching up water from the depth of the sea, is
(as appears by _Figure_ 2.) a square woodden _Bucket_ C, whose bottoms
_EE_, are so contrived, that as the weight A, sinks the Iron B, (to which
the Bucket C, is fastned by two handles DD, on the ends of which are the
moveable bottoms or Valves EE,) and thereby draws down the Bucket, the
resistance of the water keeps up the Bucket in the posture C; where