What constitutes an assault when a man raises his hand against another man in a threatening manner?

And Russell on Crime, Twelfth Edition, Volume 1, page 652: An assault, as distinct from battery, is a threat by one man to inflict unlawful force (whether light or heavy) upon another; it constitutes a crime at common law when the threatener, by some physical act, has intentionally caused the other to believe that such force is about to be inflicted upon him. The actus reus of assault thus consists in the expectation of physical contact which the offender creates in the mind of the person whom he threatens. The mens rea consists in the realisation by the offender that his demeanour will produce that expectation. The crime is constituted notwithstanding that the threatener did not intend to apply the threatened force. The anticipated contact need not be dangerous; a threat to kiss or stroke a person unlawfully would be enough. But words, however provoking, cannot of themselves amount to an assault; they may, however, have the opposite effect, for they may so qualify acts or gestures which they accompany as to explain to the other party that force is not about to be applied to him. Thus in the case of Tubervell v. Savage it was held to be no assault when A laid his hand upon his sword and said to B “If it were not assize time I would not take such language from you.” The report of this case continues, “so if he hold up his hand against another in a threatening manner, and say nothing, it is an assault.” So drawing a sword or a bayonet, or presenting a gun at a person who is within reach, or any similar act, in such circumstances as suggest an intention, coupled with an actual or apparent present ability to apply actual force to the person of another will amount to an assault provided that other is caused to believe that the force is about to be so applied. It would seem that the common law principle of assault would include a threat unlawfully to project a light, heat, electrical energy, gas, odour or any other thing on to the person of another.