Surveyors use telescopic levels to draw level surfaces and to determine the
difference in altitude between several points. In a wye (or Y) Level, the
supports for the telescope are shaped like the letter Y. This means that the
telescope can be easily removed and turned back to front. Jonathan Sisson
introduced this instrument in London in the 1720s. William Gravatt introduced
the dumpy level in 1830. Its telescope is short and fat (hence the name), and
fixed in its supports. The dumpy level is less precise but more rugged than the
wye level. A dumpy level with a small horizontal circle is known as an architect’s
or builder’s level. A precise level has a micrometer screw for adjusting the
altitude of the telescope. An automatic level uses a pendulum apparatus in place
of the bubble. This form was developed in Europe around 1950.
Other levels were designed for gunners, carpenters, masons, etc. A few of
these are in the collection.