Gunlocks: Their Introduction to the Navy
The recovery of over 2,000 gunflints of unusually large size from the wreck site of Invincible 74 gun mid-eighteenth century vessel, prompted my investigation into why she was carrying so many flints. Most flints were of 2 sizes, 37mm and 44mm at the striking edges, and were unusual because they were far larger than those used for muskets. However, after enquiries at the museum of Artillery at the Rotunda, and discussions with Seymour de Lotbiniere, author of English gun flint making in the 17th and 18th centuries, no explanation can be found as to why the Invincible's wedge-type gun flints were so large? (fig 1).
If you read through he Admiralty 'In/out' letters of this period, there are various references to authorised experiments in the fleet for both locks and tubes to improve the accuracy of gunnery afloat.

One particular letter dated 21st October 1755, named thirteen ships including Invincible, with the instruction 'quarterdeck guns of all his majesty's ships now fitting and refitting for sea to be fitted with locks, and the gunners may be supplied with a sufficient number of tin tubes for priming them'. Less than two years later, a letter from the Board of Ordnance, dated 17th August 1757, notes the decision to fit cannon locks to all of his Majesty's ships in commission.

The suggestion that that the flints for these locks were large came from a further Board of Ordnance minute dated 20th October. It suggests that any deficiency in the 'cannon' flints available could be made up by selection from the 'common musket and carbine flints' already in store.

We do not know whether the trial locks fitted to the Invinicble's 9-pounder quarterdeck guns will be found? The Court-Martial records that her quarterdeck guns were jettisoned when she first went aground. I have not been able to find any record of their recovery. However, there are various magnetometer signals to the south that may be caused by these cannon.

The consistency of the 2,000 flints recovered suggests that they originated in Kent. It is probable that they were manufactured by William Levett of Northfleet, the principal supplier of the Board's gunflints between 1742 and 1781. Flints cost 4s 6d per thousand, although larger 'wallpiece' flints were more than three and a half times the price of musket flints. The 2,000 flints represents a loss of £1 11s 6d to the crown. In France, a proposal by the Master Armourer at the Port of Toulon, suggested that firing locks tried sea-service guns as early as 1728.

Figure 1. Four sizes of gun flint from the Invincible (1758) Wreck site

However, this is predated by a letter from the Principle Officers of His Majesty's Ordnance, dated 20 July 1745, which reports unfavourably on lock trials and also refers to a similar fitting of locks to mortars some 40 years earlier. They were all condemned and sold being found quite unfit for service as I apprehend you will find this new invention will prove for firing of cannon. This shows that there is some evidence of cannon locks going back to the first decade of the eighteenth century. Admiral Steuarts writing to the Admiralty on 2 October 1747, stated that: Captain Harland is the only one at present here to whom I gave orders about the new invented locks for cannon, and from him I am in daily expectation of knowing how far they are found useful.

Figure 2. A 10 x 12 inch apron of lead from the Invicnible (1758) Wreck site.
Not unexpectedly, there was considerable opposition to their introduction in the fleet. There were complaints of the flints getting wet and failing to fire. On the subject of tin tubes, introduced at the same time to transmit the spark from the lock pan down the vent hole, Vice Admiral Hawke wrote following the Battle of Quiberon Bay on the 20 November 1759: [they are] pernicious things apt to fly out and wound the men. Two months previously, on 15 September, while on board the Ramillies, he had written to John Cleveland, Secretary to the Admiralty Board. Endorsed are seven opinions concerning cannon locks and tin tubes in mine, both of them will be very useful. Interestingly a flint from the Ramillies wreck (1760) was identical to the 2000 found in the Invincible. The practice had been to cover the vent hole with an 'apron of lead', to keep the vent dry. This was no longer possible with the new locks and explains why the flints were new locks and explains why the flints were getting wet.
Two sizes of lead aprons have been recovered from Invincible: 10 by 12 inches; and 5 ½ inches square, and these would have been useless once the locks were fitted (Figures 2 and 3). The 10 x 12 inch apron size agrees exactly with Blackmore's specification, while the 5 ½ inch square size is a slight variation on Blackmores 4 ½ x 6 inch size. Sometimes after this, a modified lead apron with a 'hump' was introduced to overcome the problem of keeping the firing mechanism dry. (figure 4). Exactly when this happened is unknown, but examples were found on the Pomone (1811) of 18lb guns and 32lb carronades.
Figure 3. A 5 ½ x 5 ½ inch Apron of lead from the Invincible wreck site
The commissioners executing the office of Lord High Admiral personally issued the precise instructions to standardise gun drill. Woe betides any Captain who failed to exercise his gun crews daily. Gunlocks certainly contributed to the supremacy of British gunnery in one important detail. They gave the Captain of the gun complete control of the moment of firing as he pulled the lock lanyard, rather than by verbally ordering his No 2 to fire with the traditional match (figure 5). As we said, all gun drill was standardised throughout the fleet. Drills were laid down for a variety of manning levels from a full crew of thirteen to a minimum of crew of six. To ensure that maximum fire rates were achieved, the crew went to quarters for gun drill every morning and the varying manning levels were exercised. It was therefore not by chance that British Naval Gunnery remained pre-eminent among the World's navies, but the painstaking attention to every detail that made the English the undisputed masters of the seas in the eighteenth century.
Figure 4 The new style apron of lead to cover a flint lock. Designed to fit a number of calibres; this one had been fitted to a 32lb carronade and was recovered from the Pomone (1811) Wreck site

The author wishes to acknowledge the help of Mr A T Mack who carried out much of the research for this paper.

1. PRO Adm 2/219
2. PRO Adm 1/52973
3. WO 50/19:20, WO 48/81:379.
4. Boudriot's letter to Mack dated 11 Jan. 1985
5. PRO Adm 1/4008
6. PRO Adm 1/916
7. H L Blackmore. The Armouries of the Tower of London, London, 1976, p. 218.