It was strong, simple, and self-contained. Metal carriages, whose claims were periodically under examination, proved brittle, too rigid, heavy, and dangerous from their liability to splinter. Gunslides, traverses, or structures laid on the deck to form a definite path for the recoil of the gun (such as the Swedish ships of Chapman’s time, for example, carried) were disliked on account of their complication, the deck-space occupied, and the difficulty which their use entailed of keeping the deck under the gun dry and free from rotting; though beds laid so as to raise the guns to the level of the ports were sometimes fitted, and were indeed a necessity in the earlier days owing to the large sheer and camber given to the decks. The use of compressors, or of adjustable friction devices, in any form, for limiting the recoil, was objected to on account of the possibilities which they presented for accident owing to the forgetfulness of an excited crew. The truck carriage, being self-contained and independent of external adjustment, was safe in this respect. The four wood trucks were of the correct form and size to give the results required. The resistance of a truck to rolling depends largely upon the relative diameters of itself and its axle. It was thus possible, by making gun-carriage trucks of small diameter and their axles relatively large, to obtain the following effect: on gunfire the carriage started from rest suddenly, the trucks skidding on the deck without rotating and thus checking by their friction the first violent motion of recoil; during the latter phase of the recoil the trucks rotated, and the carriage ran smoothly back until checked by the breechings. The friction of the trucks on the deck was also affected, however, by another feature of the design: the position of the trunnions relatively to the axis of the gun. How important was this position as influencing the history of land artillery, we have already seen. Truck guns were nearly always “quarter-hung,” or cast with their trunnions slightly below their axis, so as to cause the breech to exert a downward pressure on firing, and thus augment the friction of the rear trucks on the deck and check the recoil. The position of the trunnions was studied from yet another point of view: namely, to give the minimum of jump to the gun and ensure a smooth start to the recoil. With this object they were so placed that the two ends of the gun were not equally balanced about the trunnion axis, but a preponderance of about one-twentieth of the weight of the gun was given to the breech-end, thus bringing a slight pressure, due to deadweight alone, upon the quoin.