A “carronade” was a short, relatively light piece of ordnance capable of throwing a heavy ball at short ranges. When loaded with grape or canister rounds, they made deadly effective anti-personnel weapons.
But the carronade was a relatively new weapon, devised by the British in the 1770s.  Constitution would not be armed with large-caliber carronades on her spar deck until 1804, and it took another four years before she received a full complement of twenty 32-pounder carronades. What then, were these “carronades for the tops”? Since they were mounted high in the rigging, they had to be a fairly small, light weapons.
A letter from Secretary of War James McHenry to Captain Samuel Nicholson in April 1798 reveals who made these pieces, and at the same time leads us down the path to figuring out what they looked like:
I have no objection to the Canonades [sic] being cast for your Ship on the Plan proposed. Mr. Revere will accordingly prepare them with all convenient Dispatch.Paul Revere had already successfully completed a US government contract for ten 8-inch howitzers, four of which were intended to be mounted on Constitution’s quarterdeck. These howitzers were large guns capable of throwing a heavy explosive shell at a fairly flat trajectory, or a large amount of canister or grape shot, thereby bridging the gap between traditional broadside-mounted cannon and mortars. Unfortunately, because they had such short muzzles, both Nicholson and the gun carriage maker decided that they could not be safely mounted on the ship’s quarterdeck without cutting the gunports larger, an expensive and impracticable proposition.
It should be understood that the Canonades must undergo the usual Proof and Examinations, and will not be received if their Defects should be greater than usually tolerated.
But these new pieces were something entirely different. So far, several writers have speculated that these top guns were simply smaller versions of the large howitzers Revere had already cast. The confusion is compounded by the fact that the very term “carronade” was unfamiliar to many correspondents of the period, and they reverted to the familiar “howitzer” to describe the stubby guns.
Speculation would continue, if it weren’t for a helpfully detailed letter that Paul Revere wrote to Captain John Barry in the spring of 1798. We quote it at length because it is full of revealing information:
I take the liberty to mention to you that when Genl Knox was Secretary of War, when he was in Boston, He imployed me to go on board the French Frigate Concord, to make a drawing of the brass Carronades with their Beds, which were on her quarter deck, which I did, and transmitted to him one of the draughts, which is now in the War office at Philadelphia; they carry a Ball of the size of a 42 pr but are chiefly imployed for Grape Shot & langridge; He was so much pleased with them that he directed Tench Coxe to have 12 of them cast for the Frigate, Tench Coxe wrote me on the matter, but I afterward received a letter from him acquainting me, that Tench Francis was to provide for all Naval matters, & that I must write to him, which I did, but he never answered my letters.
Some time since Capt Nicholson wrote to the Secretary to know how his Tops were to be armed. He replied that he should send him some brass Howitzers, which carried a six pound ball; about that time Capt. Nicholson applyed to me for a drawing of a Carronade of the same size, which he sent to the Secretary of War, desiring to have them, in preference to Howitzers, & I have now orders to cast them.
If you will give yourself the trouble to examine these draughts & compare them to the Howitzers, you will see how preferable they are, & how much better for real Service. The Howitzers have their Trunions in the Centre of the Bore, which makes them dificult to Elevate or Depress, by reason that the Base, & Muzzel Rings are nearly of the same diameter; The Carronade has its Trunion, or Rather Trunion hole, directly under the Gun, by which means the Carronade is easily elevated or depress the centre of motion being so much lower—You will observe that there are Iron Cheeks to be Bolted to the upper, or Sliding bed, thro which an Iron pin is put, which secures the Carronade to the Bed; this bed is fastened to the lower one, by an Iron Pivot, which slides in a Grove made in the Under bed; which makes it quite easy to Point, either forward, or aft & very handy to load in board. Its other advantages are, it has an elevating screw thro' the Caskable, & a Ring above, to serve (?) the britching thro. Capt Nicholson was likewise directed to make use [of] 4 eight Inch brass Howitzers for his quarter deck, but upon consulting Col Claghorn, & the Carrige maker, he found his quarter deck ports were not wide enough by six or eight Inches. He has now applyed to the Secretary of War, to have four brass Carronades cast for his quarter deck, of the largest size.—Should these Guns be more agreeable to you than the Howitzers I should be happy to furnish you with them, as soon as it is possible after application is made.— my patterns are made from the small ones, & shall begin casting them to-morrow. I shall then prepare for the large ones—The Concord had a bed fitted in the Bow of the Long Boat, which shipt & unshipt at pleasure in fifteen minutes they could mount one of these Carronades in her Bows.
Six of the 8 Inch Howitzers are sent to Philadelphia, as I suppose for your ship, but as these pieces of Ordinance were never intended for the Sea, but for the land Service, I think you will not approve of them.—They are of my casting, by which you will judge of the Workmanship. 
The French frigate La Concorde visited Boston and other American ports between 1793 and 1794. What Revere saw and drew while on board that ship was undoubtedly the French model 1787 obusier de vaisseau.  Unlike the howitzers, this gun had a loop cast on the underside of the barrel, and could be elevated and depressed with a screw at the breech. In addition, it had a loop through which the breeching tackle passed.
|A French obusier de vaisseau cast at Nantes in 1794. The elevating screw and cascable ring are just peaking out behind the breech, and the iron cheeks and the pin that secures it to the bed is plainly visible. This specimen is missing the lower part of its carriage or bed, on which the upper portion could slide in for loading and our for training and firing. Musee National de la Marine, Paris|
We find further proof that this was the style of gun made by Revere. In his “cash and memoranda book” at the Massachusetts Historical Society, there’s an entry for ten carronades he cast in 1798. These weighed in total 1463 lbs. That means each piece weighed a manageable 146 lbs, and so were not large caliber guns. In addition, there’s an entry for “10 setts of iron cheek pins and screws for carronades,” suggesting they were mounted and elevated in the French fashion.
These guns remained on board Constitution until February 1800 when then-lieutenant Isaac Hull noted in his journal that they’d “Armd and Mannd the Schooner Amphitheatre and fitted her out for a 30 days cruise, Sent carpenters on board her to mount the Cannonades and Swivels sent out of the Constitution.”
It may be that one of these guns, unmarked and unidentified, is still hiding in a collection somewhere, awaiting rediscovery.
 For more on the development and evolution of the carronade, see Spencer Tucker, “The Carronade,” Nautical Research Journal, Mar. 1997.
 SecWar James McHenry to Capt. Samuel Nicholson, 21 April 1798, Naval Documents Related to the Quasi-War Between the United States and France, Vol. 1 (Washington, DC: Government Printing Office, 1935), 57.
 Paul Revere to John Barry, 29 April 1798, quoted in Martin I.J. Griffin, Commodore John Barry (Philadelphia: Martin I. J. Griffin, 1903), 340-341.
 In one letter he calls the guns “Charonades,” which sounds very much like how the French might pronounce the English “carronade.” See Renee Lynn Ernay, “The Revere Furnace, 1787-1800, thesis, University of Delaware, 1989, 34.
 Extract from journal of Lieutenant Isaac Hull, U. S. Navy, of U. S. Frigate
Constitution, Captain Silas Talbot, U. S. Navy, commanding, Friday 28 February
1800, Naval Documents Related to the Quasi-War Between the United States and France, Vol. 5 (Washington, DC: Government Printing Office, 1937), 256.