Imperfect as all non-instrumental registers must be, they nevertheless furnish some idea of the frequency of the after-shocks.
The advance over the non-instrumental observations, which latter may be termed observations of sensation, is a decided one.
Continue your non-instrumental record of the time of beginning19 and ending of the precipitation as before.
late 14c., "of the nature of an instrument," from Old French instrumental, from Medieval Latin instrumentalis, from Latin instrumentum (see instrument). Meaning "serviceable, useful" is from c.1600. Of music, c.1500; noun meaning "musical composition for instruments only" is attested by 1940. Related: Instrumentally; instrumentality.