height; they form the chief impulse of the tremendous movement, and it is they that choke from time to time the channel of the mighty torrent, and helplessly hold it in the arrest of a _block_. [Illustration: A BLOCK IN THE STRAND.] No one can forecast the moment when, or the place where, a block may happen; but mostly it occurs in mid-afternoon, at the intersection of some street where a line of vehicles is crossing the channel of the torrent. Suddenly all is at a stand-still, and one of those wonderful English policemen, who look so slight and young after the vast blue bulks of our Irish force, shows himself in the middle of the channel, and holds back its rapids with the quiet gesture of extended hands. The currents and counter-currents gather and press from the rear and solidify, but in the narrow fissure the policeman stands motionless, with only some such slight stir of his extended hands as a cat imparts to her “conscious tail” when she waits to spring upon her prey. The mute language of his hands, down to the lightest accent of the fingers, is intelligible to the dullest of those concerned in its interpretation, and is telepathically despatched from the nearest to the farthest driver in the block. While the policeman stands there in the open space, no wheel or hoof stirs, and it does not seem as if the particles of the mass could detach themselves for such separate movement as they have at the best. Softly, almost imperceptibly, he drops his arms, and lets fall the viewless barrier which he had raised with them; he remains where he was, but the immense bodies he had stayed liquefy and move in their opposite courses, and for that time the block is over.