The globes are to each other as the cubes of their radii. Their radii are the hypothenuses of rightangled triangles, of which the line of least resistance, and the semi-diameter of the excavation, are the other two sides. Therefore, to find the charge to produce any required diameter of the excavation, the following will be the rule, the radius being found as above: As the cube of the radius of the globe of compression in the following table, (having the same line of least resistance as the required globe,) Is to the cube of the radius of the required globe; So is the charge corresponding in the following table, To the charge required. _Table for the Charges of Mines, according to Valiere._ +-------------+--------------++-------------+--------------+ | Line of | Charge for || Line of | Charge for | | Least | the Mine. || Least | the Mine. | | Resistance. | || Resistance. | | +-------------+--------------++-------------+--------------+ | Feet. | lbs. oz. || Feet. | lbs. oz. | | 1 | 0 2 || 21 | 868 3 | | 2 | 0 12 || 22 | 998 4 | | 3 | 2 8 || 23 | 1140 10 | | 4 | 6 — || 24 | 1296 — | | 5 | 11 11 || 25 | 1558 9 | | 6 | 20 4 || 26 | 1647 12 | | 7 | 32 2 || 27 | 1815 4 | | 8 | 48 — || 28 | 2058 — | | 9 | 68 5 || 29 | 2286 7 | | 10 | 93 12 || 30 | 2530 4 | | 11 | 124 12 || 31 | 2792 4 | | 12 | 162 — || 32 | 3072 — | | 13 | 205 15 || 33 | 3369 1 | | 14 | 257 4 || 34 | 3680 12 | | 15 | 316 4 || 35 | 4019 8 | | 16 | 384 — || 36 | 4374 — | | 17 | 460 9 || 37 | 4748 11 | | 18 | 546 12 || 38 | 5144 4 | | 19 | 643 — || 39 | 5561 2 | | 20 | 750 — || 40 | 6000 — | +-------------+--------------++-------------+--------------+ This table is calculated upon a supposition that the excavation of the mine is a paraboloid, having a base double the line of least resistance; and that 10 lbs. 10 oz of powder is sufficient for raising one cubic fathom of earth, by making the line of least resistance of the required globe only equal to the radius of the globe of compression.