130.5 x 81 (diameter)
Wood, steel and brass

INDEX 1788 : D.V.158

Rota, ad itineris magnitudinem dimetiendam.

A wheel to measure the length of path covered.

The Gabinete de Física is privileged to possess in its collection of instruments a magnificent wheel to measure distances, signed by the English manufacturer George Adams.

The odometer has a big wheel that turns around a horizontal axle. The wheel is mounted between two arms in the shape of a fork, and has a handle at the top end which is used to manipulate the apparatus. The wheel turns around when it is in contact with the ground, activating a mechanism inside the arms of the fork. This mechanism, in turn, moves a hand on a dial near the handle. The dial is engraved with a circle calibrated from I to XII, which indicates the number of miles covered. On the inside of this circle is another calibrated scale that refers to the number of furlongs. On this second scale each group of divisions corresponds to eight furlongs. On the inside of the circle graduated in miles, are two other equal circles, both of which are numbered; the first is divided into forty parts, corresponding to a furlong, while the second is divided into a thousand parts, each representing a turn of the wheel, that is, the thousandth part of the furlong.

The following inscriptions can be found on the dial:

Numericae seu Capitales Figurae sunt Miliariae
Subdivisiones inter eas sunt Stadia
Magna Figurae sunt Pertici
Figurae Exteriores Mensuram Experiment
Catenae et Circululi Ferrei
Apud. Insig. Capite Tychonis Braheii in Vico Vulgo
Dicto Fleet Street.
Octo Stadia faciunt unum Miliariae
40 Perciti seu Decem Catenae faciunt unum Stadium
Quatuor Perciti seu 100 Circululi Ferrei faciunt unam Catenam
7 .92/100 Pollices faciunt unum Circulum Ferreum.

The numerical figures or capitals are the indication of miles.

The subdivisions between them are the furlongs.
The big figures are the perches,
and the outside figures mark the measurement of the chain
and of the little iron circle.
     George Adams,
made the odometer at a place called Tycho Brahe in Fleet Street, London.
Eight furlongs in a mile
Forty perches or ten chains in a furlong
Four perches or a hundred iron circles in a chain
Seven 92/100 inches in an iron circle.

From Colégio dos Nobres, catalogue n.º 149.

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