The extreme relief we find in some old barrels is certainly not required; but still it clearly shows that the principle was understood and acted upon: the very extreme has been produced by ignorance, as certainly as the suggestion was a proof of knowledge on the part of the suggestor; for many think, if a small dose is good for a patient, a large one must be equally so. Like ourselves of the present day, having discovered that fine gunpowder was advantageous, we have carried the principle so far as undoubtedly to overstep the line to which it was beneficial we should advance; thus clearly establishing the truth of the old adage, “One extreme begets another.” Therefore, in advocating the adoption of gun-barrels of the very essence of iron, I also say, let that part of the tube whose duty is the generating of force be nearly cylindrical, and let there be a gradual expansion of the bore for a few inches in approaching the muzzle, that the restraint of the lateral pressure may not be too rapidly loosened. But yet let that expansion be so graduated that there shall not be an extreme either way--only a scarcely perceptible relief; yet such as will influence and prevent the divergence of the projectiles to a considerable extent. Blaine says--“A very long barrel is liable to have the force of its discharge lessened by the increase of counter pressure in the greater volume of internal air in a long than in a short barrel.” The column of air in the barrel is unquestionably calculated to lessen the force of the discharge. But I have already shown that this is completely controlled by the system of granulation. Further, he says--“Its force must also suffer by the loss which the elasticity of the propelling gas experiences in its lengthened transit through an extended range of barrel.” He is here supposing an instantaneous generation of force, which cannot possibly happen; and if it did, would be comparatively useless. But he is evidently on the right scent, if he could only follow it up. Again,--“In such cases, it is probable, that the shot, which should leave the mouth of the piece at the instant when the propelling force has gained its maximum, in a long barrel are detained beyond that particular limit of capacity we have pointed out as inherent in each barrel; and which properties, and which quantities of charge, nothing but repeated and varied trials can teach the owner of the gun.”