Fine all brass example of the calculating sector which
was described in 1623* by Edmund Gunter (1581-
1626). The engraved letter forms are clearly in a 17th.
century hand, such as that of Elias Allen (1606-1654).
Except for the absence of a few words, it is remarkably
similar to the sector as described by Gunter. A fine
example of a very early English Mathematical Instrument.
In very good condition. Length closed 9.75 inches
(25cms), open 18.25 inches (46cms). English, mid 17th.
century. Ticket Price £1800.
A siren of the type described in 1819 by Baron Charles Cagniard De la Tour
(1777-1859. A sound is produced by forcing air through slanted holes in the
rotor. If the number of holes is known then the frequency can be determined
by the number of revolutions (indicated on the dials) and the duration of
rotation. The stops protruding from the side of the air chamber control a
series of concentric ring that can be moved to allow various combination of
holes to be used. This was invented in 1851 by Wilhelm H. Dove (1803-79).
