The story of the carronade begins some little time before the meeting of the Carron board in the year 1778. It will be remembered that in 1747 Mr. Benjamin Robins had advocated, in a much-talked-of paper, an increase in the calibre of warships’ guns at the expense of their ranging power, and that in support of his argument he had drawn attention to two features of ship actions—first, that the great majority of duels were fought at close quarters; secondly, that the destructive effect of a cannon-ball against an enemy’s hull depended largely on the external dimensions of the ball, the larger of two balls producing an effect altogether out of proportion to the mere difference in size.

However invalid may have been the arguments founded on these assertions—and that there was a serious flaw in them time was to show—there could be no doubt that, so far as considerations of defence were concerned, the conclusions reached were of important value. In the case of a merchant packet defending herself from boarding by a privateer, for example, a light, short-ranging gun throwing a large ball would give far more effective protection than a small-calibre long gun. And if, moreover, the former involved a dead weight less than a quarter, and a personnel less than half, of that involved by the latter, the consideration of its superiority in action was strongly reinforced, in the opinion of shipowners and masters, by less advertised considerations of weight, space, and equipment—very important in their relation to the speed and convenience of the vessel, and hence to all concerned.

So the arguments of Robins, though propounded solely with reference to warships, yet applied with special force to the defensive armament of merchant ships. A conception of this fact led a very able artillerist, General Robert Melville, to propose, in 1774, a short eight-inch gun weighing only thirty-one hundredweight yet firing a nicely fitting sixty-eight pound ball with a charge of only five and a half pounds of powder. This piece he induced the Carron company to cast, appropriately naming it a Smasher. Of all the carronades the Smasher was the prototype. It possessed the special attributes of the carronades in the superlative degree; the carronade was a reproduction, to a convenient scale, of the Smasher. That General Melville was the prime inventor of the new type, has been placed beyond doubt by the inscription on a model subsequently presented to him by the Carron Company. The inscription runs: “Gift of the Carron Company to Lieut.-General Melville, inventor of the Smashers and lesser carronades for solid, ship, shell, and carcass shot, etc. First used against French ships in 1779.”[85]

In almost every respect the Smasher was the antithesis of the long gun: the advantages of the one were founded on the shortcomings of the other. For instance, the smallness of the long gun’s ball was a feature which, as ships’ sides came to be made stronger and thicker, rendered the smaller calibres of long guns of a diminishing value as offensive armament. It was becoming increasingly difficult to sink a ship by gunfire. The round hole made near the enemy’s water-line was insufficient in size to have a decisive effect; the fibres of the timber closed round the entering shot and, swelled by sea-water, half closed the hole, leaving the carpenter an easy task to plug the inboard end of it. The large and irregular hole made by a Smasher, on the other hand, the ragged and splintered opening caused by the crashing of the large ball against the frames and timbers, was quite likely to be the cause of a foundering. Again, the high velocity of the long gun’s ball, while giving it range and considerable penetrative power, was actually a disadvantage when at close quarters with an enemy. The maximum effect was gained, as every gunner knew, when the ball had just sufficient momentum to enable it to penetrate an opponent’s timbers. The result of a high velocity was often to make a clean hole through a ship without making a splinter or causing her to heel at all. Hence the practice of double-shotting: a system of two units which, as we have just seen, was less likely to prove effective than a system of a larger single unit. On the other hand the Smasher vaunted its low muzzle velocity. As for the relative powder charges, that of the long gun was wastefully large and inefficient, while that of the Smasher was small and very effective. It was in this respect, perhaps, that the Smasher showed itself to the greatest advantage. And as this feature exerted from the first an important influence on all other types of ordnance, we will examine in some detail the means by which its high efficiency was attained.

Apart from the inefficiency inherent in the small-ball-and-big-velocity system the long gun laboured under mechanical disadvantages from which its squat competitor was happily free. In the eighteenth century the state of workshop practice was so primitive as to render impossible any fine measurements of material. Until the time of Whitworth the true plane surface, the true cylinder and the true sphere were unattainable in practice. For this reason a considerable clearance had to be provided between round shot and the bores of the guns for which they were intended; in other words, the inaccuracies which existed in the dimensions of guns and shots necessitated the provision of a certain “windage.” But other considerations had also to be taken into account. The varying temperatures at which shot might require to be used; the fouling of gun-bores by burnt powder; the effect of wear and rust on both shot and bore, and especially the effect of rust on the shot carried in ships of war (at first enlarged by the rust and then, the rust flaking or being beaten off with hammers, reduced in size)—all these factors combined to exact such disproportionate windage that, in the best conditions, from one-quarter to one-third of the force of the powder was altogether lost, while, in the worst conditions, as much as one-half of the propulsive force of the powder escaped unused. Not only was a large charge required, therefore, but the range and aim of the loosely fitting shot was often incorrect and incalculable; the motion of the shot was detrimental to the surface of the bore and the life of the gun; while the recoil was so boisterous as sometimes to dismount and disable the gun, injure the crew, and even endanger the vessel.

The inventor of the Smasher, by eliminating this obvious deficiency of the long gun, gave to his weapon not only a direct advantage due to the higher efficiency of the powder-charge, but also several collateral advantages arising from it, such as, economy of powder, ease of recoil, and small stresses upon the mounting and its supporting structure.

It had been laid down by Dr. Hutton in 1775, as one of the chief results of the systematic experiments carried out by him at Woolwich in extension of the inquiries originated by Robins, that if only the windage of guns could be reduced very important advantages would accrue; among others, a saving of at least one-third of the standard charges of powder would result. General Melville determined to give the Smasher the very minimum of windage necessary to prevent accident. The shortness of the bore favoured such a reduction. The large diameter, though at first it might appear to render necessary a correspondingly large windage, was actually an advantage from this point of view. For, instead of adhering to the orthodox practice with long guns, of making the windage roughly proportional to the diameter of the bore, he gave the Smasher a windage less than that of a much smaller long gun, arguing that though a certain mechanical clearance was necessary, yet the amount of this clearance was in no way dependent on the diameter of the shot or piece. The large size of the Smasher acted therefore to its advantage. The windage space through which the powder gases could escape was very small in relation to the area of the large ball on which they did useful work.

But this divergence from the standard practice would appear to necessitate the provision of special ammunition for use with the Smasher: the nicely fitting sixty-eight pound ball would require to be specially made for it? And this would surely militate against the general adoption of the Smasher in the public service? No such difficulty confronted the inventor. For, curiously enough, the principle on which the dimensions of gun-bores and shot were fixed was the reverse of the principle which obtains to-day. Instead of the diameter of the gun being of the nominal dimension and the diameter of the shot being equal to that of the gun minus the windage, the diameter of the shot was the datum from which the amount of the windage and the calibre of the gun were determined.

So, the size of the shot being fixed, a reduction of windage was obtainable in a new design of gun by boring it to a smaller than the standard diameter. And this was what the inventor of the Smasher did. The large ball, in combination with the restricted windage and the small charge of powder, gave the Smasher ballistic results far superior, relatively, to those obtained with the long gun. Its lack of ranging power was admitted. But for close action it was claimed that it would prove an invaluable weapon, especially in the defence of merchant ships.[86] Not only would its large ball make such holes in the light hull of an enemy privateer as would break through his beams and frames and perhaps send all hands to the pumps; but, projected with just sufficient velocity to carry it through an opponent’s timbers, it would thereby produce a maximum of splintering effect and put out of action guns, their crews, and perhaps the vessel itself.

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