All 6 Uses of

herald
in
Jane Eyre

I can now conjecture readily that this streak of light was, in all likelihood, a gleam from a lantern carried by some one across the lawn: but then, prepared as my mind was for horror, shaken as my nerves were by agitation, I thought the swift darting beam was a herald of some coming vision from another world.
p. 21.2 *

herald = sign

Those who want situations advertise; you must advertise in the —shire Herald.
p. 103.4

herald = the name of a newspaper that indicates that the newspaper announces news

Replies rose smooth and prompt now: "You must enclose the advertisement and the money to pay for it under a cover directed to the editor of the Herald;"
p. 103.5 *

If J.E., who advertised in the —shire Herald of last Thursday, possesses the acquirements mentioned, and if she is in a position to give satisfactory references as to character and competency, a situation can be offered her where there is but one pupil, a little girl, under ten years of age; and where the salary is thirty pounds per annum.
p. 105.2

It had been a mild, serene spring day — one of those days which, towards the end of March or the beginning of April, rise shining over the earth as heralds of summer.
p. 193.4

heralds = announcers

It was as if I had heard a summons from Heaven -- as if a visionary messenger, like him of Macedonia, had enounced, "Come over and help us!" But I was no apostle, — I could not behold the herald, — I could not receive his call.
p. 464.1

herald = announcer of important news

Definitions:

(1) (herald as in: heralds the coming of...)
a sign that something will happen -- especially something important and good

or:

to announce or welcome -- especially with enthusiasm
(2) (herald as in: announced by herald & trumpet)
a person who announces important news -- especially a king's representative
(3) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

More rarely, herald can also refer to an official whose specialty is heraldry (the study of coats of arms -- symbols once used to signify the right to bear arms).

Historically a herald was a person who made announcements at jousting matches, or (much more rarely) any prestigious assistant in a dignified setting such as a courthouse or royal palace.