To speak by the card

to speak from information and definitely, not by guess as in telling a ship's bearing by the compass card.

See also: Card

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
Mentioned in ?
References in classic literature ?
At any rate, it was more like a hearse than any thing else, though to speak by the card, it was a gondola.