be perfectly straight in the inside; if not, to make them so. The necessity of great care and attention to this point, must be very obvious; for, if not perfectly correct at this stage, it will require more skill and time to get it correct afterwards than the generality of barrel-makers are inclined to bestow. When the inside has been found to be all right, the barrel is ready for grinding. Many barrel-makers turn their barrels entirely by self-acting lathes, and thus obtain a correct taper from breech end to muzzle. Experience has clearly convinced us that this is not the best shape, but slightly hollow towards the muzzle is preferable, as additional weight there is decidedly injurious, and the shooting of barrels of lighter construction is decidedly better. The generality of Birmingham barrels are ground to the size required on large stones, which revolve at a terrific rate. The skill acquired by many of the workmen is astonishing. Over and over again, have we seen barrels coming from the mill put into the lathe, and found almost as true as if they had been turned. They have a method of allowing the barrel to revolve in their hands at half the rate of the stone, and by this means they grind them so fine that many would be puzzled to determine whether they had been turned or ground, were the barrel smoothed lengthways merely to take out the marks of the stone. We have seen the squares of a rifle barrel ground to as perfect an octagon as the eye could assist in forming. Best barrels are generally turned after they are ground. Inferior barrels are struck up with a large rubber, or smooth, by boys; in some instances by women. There is one advantage derived from grinding barrels, namely, that the friction of the stone being continuous, the temper of the barrel is not so much affected as where the tool in the slide-rest is cutting a considerable portion at once; for all barrels are best, and superior to their compeers, which require least metal to be either ground or turned off their surface, as there is a density on the outer which is not in the interior portion. The harder the material, the less the extent of this objection.