If in every story of a building four or five courses are thus laid and fortified, a great deal of strength is given to the structure.  Another method, which has rather fallen into disuse, is grouting.  This is pouring liquid mortar, about the consistency of gruel, upon the work at about every fourth course.  The result is to fill up all interstices and cavities, and to delay the drying of the mortar, and brickwork so treated sets extremely hard.  I have seen a wall that had been so treated cut into, and it was quite as easy to cut the bricks (sound ones though they were) as the mortar joints.

Grouting is objected to because it interferes with the good look of the work, as it is very difficult to prevent streaks of it from running down the face, and it is apt to delay the work.  But it is a valuable means of obtaining strong brickwork.  Another and a more popular method is to build the work in cement, now usually Portland cement.  This, of course, makes very strong, sound work, and does not involve any delay or dirt like grouting, or the introduction of any fresh material like hoop iron.  But it, of course, adds to the expense of the work considerably, as cement is much more costly than lime.  I ought to add that the advocates of Scott’s selenitic mortar claim that it not only sets quickly and hard, but that it is extremely tenacious, and consequently makes a much more robust wall than ordinary mortar.  I dare say this is true; but I have not happened to see such a wall cut into, and this is the best test of solidity.

The second deficiency in brickwork which I am bound to notice is that, though it is very fireproof, it is far from being waterproof.  In an exposed situation rain will drive completely through a tolerably stout brick wall.  If water be allowed to drop or fall against it, the wall will become saturated like a sponge.  If the foot of a wall becomes wet, or if the earth resting against the lower parts of it be moist, water will, if not checked, rise to a great height in it, and if the upper part of the wall be wet, the water will sink downward.  With most sorts of brick the outer face absorbs moisture whenever the weather is moist; and in time the action of the rain, and the subsequent action of frost upon the moisture so taken up, destroys the mortar in the joints, which are to be seen perfectly open, as if they had been raked out, in old brickwork, and in some cases (happily not in many) the action of weather destroys the bricks themselves, the face decaying away, and the brick becoming soft.

Against this serious defect in our staple building material a series of precautions have been devised.  Damp rising from the foot of the wall, or from earth lying round its base, is combated by a damp course—­a bed of some impervious material going through the wall.  Damp earth may be kept off by surrounding the walls with an open area or a closed one—­usually termed a dry area.  Damp against the face of the