AMERICAN INSTITUTE. 589 



ing fresh lime with water, and pouring it while hot, among the 

 masonry in the body of the wall. The walls called by the 

 Greeks Isodomum, are those in which all the courses are of an 

 equal thickness, and the Pseudo-Isodomum, are those in which 

 they are unequal — both these walls are firm. In the kind of 

 walls called amplection by the Greeks, the faces are all built with 

 dressed stones, with the other sides left rough; and the two faces 

 were secured by occasional bond stones. Walls entirely of hewn 

 stone may be made one-fifth thinner than those of brick. A wall 

 should be reduced in thickness as it rises, for the same reason 

 that a column is diminished, and if the wall be a part of the 

 house, it should be reduced in a greater degree by internal offsets. 

 In building a wall, impervious to heat and moisture, the first pre- 

 caution that is required, is to dig deep enough to ascertain the 

 nature of the ground and of moist to guard against it; the next 

 to lay a sufiiciently extensive and firm foundation. The disposi- 

 tion of the stones or bricks is of much importance, as the strength 

 is greatest when all the surfaces are either horizontal or vertical. 

 If they be oblique, they must have a tendency to slide away lat- 

 erally, and the wall be liable to crack. It is not of much advan- 

 tage in walls to use stones which have a greater length than three 

 times their thickness; otherwise from the difficulty of binding 

 them equally, they are. liable to break in the wall. It is not un- 

 usual in building to make the external of an inclosing wall of 

 hewn stone, and the internal part of rubble work; but these set- 

 tle unequally, and wliere the walls support much weight danger- 

 ous cracks and bulges take place. The walls of St. Peter's church 

 at Rome, show some serious defects arising from this cause ; such 

 walls are not impervious to heat and moisture. 



A wall should be so constructed that the resultant of the pres- 

 sures should everywhere fall within the thickness of the wall ; 

 and a careful investigation of this problem will show that a curved 

 wall is the strongest possible. If a plain wall be not thick 

 enough to admit a curve to be drawn within it, there will be a 

 tendency to bulge at one-third of the height from the base. The 

 utility and common practice of building nearly all our (edifices of 

 brick, arises from motives too obvious to need a definition; since 

 it is generally considered to be much the cheapest, as well as the 

 most eligible substance that can be invented for the purpose, both 

 in point of beauty and duration, and inferior to nothing but 

 wrought stone. The use of bricks, in buildings, may be traced 

 to the earliest ages, and they are found among the ruins of almost 



