Heaven preserve us!
Would that better feelings moved them!
O Lord, be merciful unto me, a sinner!
Interjections are not always followed immediately, and are sometimes not allowed at all, by a mark of exclamation. No rule can be given more precise than this: (1) That we should not insert a mark of exclamation immediately after an interjection, unless we should make a distinct pause after it in speaking; and (2) that no mark of exclamation is to be used at all, unless the exclamatory nature of the sentence is more or less strongly marked. It is useful to notice the difference between "O" and "Oh." The former is used only before the vocative case, and never has a mark of exclamation, or indeed any point, placed immediately after it.
Alas! all our hopes are blasted.
Lo, he cometh!
O Dido, Dido, most unhappy Dido!
Unhappy wife, still more unhappy widow!
Oh, do not reckon that old debt to my account to-day!
XXXV. The mark of exclamation is placed after sentences which, though interrogatory in form, are really exclamatory.
How could he have been so foolish!
And shall he never see an end to this state of things! Shall he never have the due reward of labour! Shall unsparing taxation never cease to make him a miserable dejected being, a creature famishing in the midst of abundance, fainting, expiring with hunger's feeble moan, surrounded by a carolling creation!
This rule might be put in another way by saying that a mark of exclamation, and not a point of interrogation, is placed after what are called rhetorical questions, or statements made more striking by being put in the form of questions. They are not asked for the sake of receiving a direct answer, and are in reality exclamations. Still all rhetorical questions are not thus punctuated; the point of interrogation is sometimes more effective. The sentences quoted under [Rule XXXI.] would lose much of their force if marks of exclamation were used. In each case we must decide whether the sentence strikes us most as a question or as the expression of emotion.
XXXVI. The mark of exclamation is sometimes placed after an ironical statement.