and its density might be ascertained by means of a watch and a
small instrument, in which the number of turns made by a vane
moved by a constant force, should be registered. The less dense
the air in which the vane revolves, the greater will be the
number of its revolutions in a given time: and tables could be
formed from experiments in partially exhausted vessels, aided by
calculation, from which, if the temperature of the air, and the
number of revolutions of the vane are given, the corresponding
height of the barometer might be found.(1*)

NOTES:

1. To persons who may be inclined to experiment upon this or any
other instrument, I would beg to suggest the perusal of the
section 'On the art of Observing', Observations on the Decline of
Science in England, p. 170, Fellowes, 1828.



Chapter 4

Increase and Diminution of Velocity

32. The fatigue produced on the muscles of the human frame
does not altogether depend on the actual force employed in each
effort, but partly on the frequency with which it is exerted. The
exertion necessary to accomplish every operation consists of two
parts: one of these is the expenditure of force which is
necessary to drive the tool or instrument; and the other is the
effort required for the motion of some limb of the animal