TEXT:
HORATIO
Stop it, Marcellus.
The cock crows.
MARCELLUS
Shall I strike at it with my partisan?
HORATIO
Do, if it will not stand.
BERNARDO
'Tis here!
HORATIO
'Tis here!
MARCELLUS
'Tis gone!
Exit Ghost
We do it wrong, being so majestical,
To offer it the show of violence;
For it is, as the air, invulnerable,
And our vain blows malicious mockery.
BERNARDO
It was about to speak, when the cock crew.
HORATIO
And then it started like a guilty thing
Upon a fearful summons. I have heard,
The cock, that is the trumpet to the morn,
Doth with his lofty and shrill-sounding throat
Awake the god of day; and, at his warning,
Whether in sea or fire, in earth or air,
The extravagant and erring spirit hies
To his confine: and of the truth herein
This present object made probation.
NOTES:
The Cock Crows
Stage directions are notoriously unreliable in Shakespeare's texts. Very often they are the estimation of editors, trying to remember where things might have happened on the stage in performances they may or may not have even seen! The Folio doesn't have any suggestion at all for where the herald of the morn may sound, but I think it needs to be as late as possible to get as much dramatic tension as possible. We should feel as the audience that the Ghost might indeed be about to speak, only to be thwarted and have to retreat when the bird sings.
Partisan
A partisan is a particularly medieval-looking weapon consisting of a large spear-head mounted on a pole. It would be very characteristic of a knight's weaponry in the Middle Ages, and indeed they are still carried by the Beefeaters in the United Kingdom.
Phoebus Apollo
Apollo was the god of light for the Greeks and Romans - interestingly he is one of very gods whose name was the same in both cultures. Although he had many charges and was the god of many things (healing, music, knowledge, medicine, archery, and the arts, to name but a few) it was as the god of the sun and therefore as Bright Apollo that he was most frequently mentioned and invoked. Shakespeare here refers to him as 'the god of day'.
Basilisk
I got a little carried away mentioning the basilisk, the mythical serpent ('king' of snakes) that is so dangerous it can kill you by looking at you. The creature shows up in literature from the works of Venerable Bede to the Canterbury Tales, and from Leonardo da Vinci all the way to Harry Potter! There are numerous references to the basilisk in Shakespeare also, invariably to do with this lethal gaze.