Percentage unit of angular measurement, with logarithms; also a description of his percentage theodolite and percentage compass, for the use of surveyors, navigating officers, civil and military engineers, universities and colleges

1912·23.1 MB·English

by  Fergusson, John Coleman

FERGUSSON'S
TP~*\ YE~"^ TR""\ /C"""NE1 "* NX 1Tf~T^AA Gs .E1 i Ur TNT* I7 T
AN G R MBASU REMENT
IJ I .A
WITH
LOGAITHMS FOR ITS US
AND FOR
EGREES. MlNUTliS AND SECONDS
JOHN I^RGUSSON
C.
M. JNST. C. E.

FERGUSSON'S PERCENTAGE UNIT
OF ANGULAR MEASUREMENT,
WITH LOGARITHMS.
THE MIDLAND COUNTIES HERALD LTD..
16, UNION STREET,
BIRMINGHAM.

PLATE
I.
T T20 Mi <i Mi -6i0, 7=%^~8i 9tr
t 'figure explains the construction of Fergusson's Percentage Circle by
showing the tangent scales to the octants.
Thiscircle isattachedto the Percentage Theodolite and to Magnetic Compass-
dtals togetherwitha concentric circle dividedintodegrees. Each circle can be
read &y two separate andopposite indices, either in percentage units or degrees.
Thiscircle willconvert any angularinstrumentintoamostsimpleandaccurate
range-finder.