in general, whatever is subservient to a cause in producing any effect.

Mathematical, Philosophical, &c. INSTRUMENTS. See Astronomy, Electricity, Geometry, Levelling, Mechanics, Optics, Pneumatics, &c., &c.

Instrument, is also used in law, to signify some public act, or authentic deed, by means whereof any truth is made apparent, or any right or title established, in a court of justice.

Notarial Instrument, in Scots Law, any fact certified in writing, under the hand of a notary-public.