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.

Insubrium ager, (anc. geogr.), a district of the Transpadana; situated between the Ticinus to the west, the Addua to the east, the Padus to the south, and Orobii to the north. The people called Insubres by Livy, Insubri by Ptolemy, and Iombres by Strabo. Now the Duchy of Milan.

Insular, anything belonging to an island.—Insubrian situations are productive of many happy consequences to the inhabitants, both with respect to the climate, security, and convenience for commerce; for a particular account of which, see Island and Coast.