BLOCKHOUSE is to a temporary fortification what a tower is to one that is perma nent. Ina wooded country, it is easily and quickly made, and the enemy cannot readily bring guns to bear upon it; on flat open ground it is less useful. The B. is always a covered defense, unlike a battery; sometimes with only one story, sometimes with two, of which the lower forms a barrack for a few men. It is usually either rectangular or &aped like a Greek cross; the latter is preferred, as enabling the fronts of fire to flank arch other. The defense is usually by musketry. If opposed to infantry only, single rows of trunks of trees, either upright or horizontal, make a very good R, loopholed ert intervals of about 3 ft.; and if there be earth enough quickly obtainable, by digging a ditch or from any other source, to embank it all round and to cover the roof, it will bear a great deal of rough usage. If opposed to artillery, the B. requires to be
formed with double rows of trunks three feet apart, with well-rammed earth between them. The American backwoodsmen build blockhouses with great quickness and efficiency; several of these, with a curtain or continuous wall of stockading, may be made to inclose a large space, capable of accommodating a great number of defenders, and of repelling a considerable hostile force. The base of a wind-mill, on a hill, has in European countries often formed a good blockhouse. A regular B. should have a ditch, not only to supply earth, but to keep the enemy from approaching near enough to fire the timber of the blockhouse. There must be, at least, 4 ft. of well-rammed earth on the roof, to resist the effect of artillery. Such a structure without a roof is not a B., it is simply a stockade.