imperceptible

an imperceptible drop in temperature.

The slight change in the taste was imperceptible to most people.

She answered with an almost imperceptible nod of the head.

His head moved in an almost imperceptible nod.

Imperceptible, we beside this once soporous elephant, begin to send force already.

It may well be called the Concord, the river of peace and quietness;for it is certainly the most unexcitable and sluggish stream that ever loi¬tered imperceptible towards its eternity—the sea.