A good brick, suitable for piers and heavy work, should not break under a crushing load of less than 4,000 pounds per square inch; any additional strength is not of great importance, provided the brick meets the preceding requirements. In a wall the transverse strength is usually of more importance than the crushing strength. For a good brick the modulus of rupture should not be less than 720 pounds; or, in other words, a brick 8 inches long, 4 inches wide and 2 inches thick should not break under a centre load of less than 1,620 pounds, the brick laying flatways and having a bearing at each end of 1 inch and a clear span of 6 inches. A first-class brick should carry 2,250 pounds in the centre without breaking, and bricks have been tested which carried 9,700 pounds before breaking.