Bricks . 
157 
the first course fit into the grooves of the second, and the shoulders 
of the second fall into the grooves of the first, thus forming an in- 
dented line of nearly equal divisions. The grooves, however, 
ought to be somewhat wider than the two adjoining shoulders, to 
allow for mortar, See. The construction of these bricks is perfect- 
ly simple ; but the principle will be preserved, in whatever form 
of indenture they may be made to lock into, or cramp each other. 
Brick walls, constructed upon this principle, require no bond tim- 
ber ; one universal bond connecting the whole building, which can 
neither crack nor bulge out without breaking through the bricks 
themselves. This invention is also particularly useful in the con- 
struction of arches ; and when employed for this purpose, the 
shoulders of the bricks and the sides of the grooves should be 
radii of the circle, of which the intended arch is a segment. It is, 
however, recommended, that if the arch be particularly fiat, or ap- 
plied in situations which do not admit of end walls, to have the 
shoulders dove-tailed, to prevent the arch cracking across, or giv- 
ing way edgewise. In forming an arch, the bricks must be coursed 
across the centre, and a grooved side of the bricks must face the 
workmen. The bricks may be either laid in mortar, or dry, and 
the interstices afterwards filled up by pouring in lime-putty,* Paris 
plaster, or any other convenient material. The obvious advanta- 
ges of arches constructed upon this principle, are, that the same 
centre, which, whatever be the breadth of the arch, may be in no 
case many feet wide, may be regularly shifted as the work pro- 
ceeds ; and as they have no lateral pressure, they require no 
abutments to prevent their expanding at the foot, nor any weight 
upon the crown to prevent their springing up. They may be laid 
upon a common perpendicular wall, and if used in the construc- 
tion of common buildings, they will not only preclude the neces- 
sity, and save the expence of timber, but will also afford an abso- 
lute security against the possibility of fire. 
A new invention in the formation of bricks, by M. Legressier, 
has lately been announced in the Archives des Decouvertes et des 
Inventions JVouvelles , pendant Vannee 1 809. The principle, how- 
ever, is merely that of Mr. Cartwright’s, followed out to a greater 
extent than has perhaps ever been done in this country. M. Le- 
gressier proposes, that the bricks should be formed in seven dif- 
ferent moulds, according as they are to be placed in the middle 
or on the exterior of the walls ; in the bottom or on the top ; in 
the arches or in the corners : and by the proper disposition of 
these bricks in the building, every pressure, either longitudinally 
* €3 routing* 
