For lining cupolas for blast furnace or other cupreous slags, nothing is better than Dinas bricks unless it be gauister bricks as made at Lowood near Sheffield. The only difference between the two is the quantity of silica contained in each. A good Lowood brick has assayed out at the following proportions: Silica, 96.4; alumina, 1; lime, 125; sundry oxides, 1.35; while a best Dinas brick from Wales assayed out as follows: Silica, 95.75; alumina, .4; lime, 3; sundry oxides, .85. Ganister bricks do not, on cooling, crack so quickly as Dinas bricks, because Dinas bricks, having a higher percentage of silica, are practically infusible and unaffected by the great heat. The bricks, either Dinas or ganister, should be set in the very thinnest of ganister cement, the usual plan being to dip the brick in very thin cement, and when the work is finished to slurry over the surface with thin cement.