We all start with the description given by Bowen: "Mr. Brown immediately resolved on her destruction, and he forthwith directed one of his trusty shipmasters to collect eight of the largest long-boats in the harbor, with five oars to each..."

This 18th century description is a strange description to modern city dwellers, because "five oars" is an odd number, not an even number of oars, and we assume that rowing takes an even number of oars.  At first one perhaps thinks that Bowen wants to tell us that the fifth oar was used for steering  (which does not make much sense because long-boats steered by a tiller, as was often the case, would be better for the purpose of the attack).  Then we think that Bowen wants to tell us the fifth oar was to be a spare. (That does not make much sense, because the persons whom he was addressing really would not care whether a spare oar was carried). And since we do not know by experience what an ordinary long boat of the day was, we cannot picture in our mind the size involved, so "largest" doesn't seem to help us much without some further digging. Most of us today stop after reading Bowen's description and do not spend time thinking about what it means.

"Five oars" does say something about the size of the boats if the audience is composed of 18th century persons familiar with ship's boats use, and, on close examination, Bowen's "largest" description does tell us even more about the size of the boats.

In the 18th Century,  the nautical term of "oars" when describing a boat,  could mean either "single oars" or "pairs of oars".  For an example of the use "oars" to mean "pair of oars", see the Table of Boats carried by British vessels of war by William Mountaine, The Seaman's Vade-Mecum (London, 1757).  British warships carried a variety of small boats, for different purposes.  Mountaine describes the oars of the various "Long Boats" as e.g., "7 oars" or 8 oars"  Yet, if you look at the same type of long-boats in the British Navy drawings,  you will see the oars set out as "7 Pair" or  "8 Pair".  E.g., "18th Century Longboats After Chapman", at Notes on 18th Century Ship's Boats, Vol.  26, Nautical Research Journal, p 209 et seq. (Nautical Research Guild, Washington, D.C., Dec., 1980).

It is at least equally probable, just from the use of the term alone, that Bowen was describing long-boats that had what we would call "five pairs of oars".

What we can deduce from the necessary size of a rowed boat with 5 pairs of oars is a boat that has at least 3 feet of length for each set of oars.  Therefore, considering some room at the bow and some at the stern, in addition to the space for 5 seats for rowing, the longboats must have been in excess of 18 feet long.

This estimate of the minimum size of the longboats (calculated from a meaning of "five pairs of oars") of which Bowen was speaking, fits with Bowen's adjective "largest" in "largest long-boats", if we examine the usual size of a long-boat of the day.

William Falconer, in Universal Dictionary of the Marine (London 1789) defines types of boats as the terms were used in the 18th Century, and defines a "longboat" as: the largest boat that usually accompanies a ship, and is generally furnished with a mast and sails, and further describes the longboat as what is common to a merchant-ship.

See the accompanying diagram of a "6 Pair" of oars longboat of the 18th Century. (Click to enlarge the thumbnail.)  Note it is 22 feet long and over 7 feet wide. 

Likewise, the U.S. Tables of Allowances for the outfitting of our Naval ships at the beginning of the 19th Century, providing for various boats for the ships, are instructive.  The sloops and brigs had accompanying boats of  from 21 to 30 feet in length. See Vol. 31, Nautical Research Journal, p 47 et seq.  (Nautical Research Guild, Bethesda, MD 1985). Again , this suggests that Bowen's "largest long-boats" were easily in excess of 20 feet long.

Bowen's account suggests that the his seat was wide enough for another person to be in the middle (not rowing): "I took my seat on the main thwart, near the larboard [left hand side if facing forward in a boat] row-lock, with my gun by my right side, facing forwards. As soon as Dudingston began to hail, Joseph Bucklin, who was standing on the main thwart by my right side,...."

The persons rowing necessarily cannot be tight against the outside of the boat if there is to be any effective rowing.  A rower needs a two to three foot width of room to row. Two rowers with enough room for a third man to stand on the rowing thwart yields a width of 7 feet or so.

The existing drawings of longboats of the era  indicate a rather uniform ratio of length, breath, and depth.  This is not surprising, since the colony's and the English shipbuilders knew enough to build on experience and had a body of experience on which to build.  Assuming even a 7 foot width, from Bowen's description of where Joseph Bucklin was standing, and assuming 18th Century standard length to breath dimensions, would yield a longboat length in excess of 18 feet.  Again, this suggests that Bowen's "largest long-boats" were easily in excess of 20 feet long

What was the group of ships from which Brown could requisition eight longboats?  By 1772,  the Browns of Providence were engaged in slave trading in Africa and whale hunting in the Atlantic Ocean.  Ships used in both of these enterprises needed more than a small row boat.  For the trading, it was common to anchor relatively far off a shallow shore without a harbor and send the boats back and forth to transport the goods.  For whale hunting, a substantial boat with a number of men rowing was needed to quickly reach and harpoon and tow the whales. If John Brown really asked for the largest longboats available to him in the harbor, one would not expect a 15 foot rowboat with only 5 single oars to be furnished to him.  Indeed, Brown knew that the attacking force would have to row at 6 miles against the tide, and that the final approach might need speed.  Four men rowing an overloaded boat would not be what a sailor (and these men were sailors) would use for such an expedition.  The boats both available and desirable to Brown would have been capable of large carrying capacity and would have been able to carry 10 men rowing and 1 man steering without difficulty.  Again , this suggests that Bowen's "largest long-boats" were easily in excess of 20 feet long

The attacking force clearly impressed the Gaspee officers and men as being overwhelming is size.  Their estimates were well over a 100 attackers. (E.g., Dickinson said that in the three boats that initially boarded there were 30 or 40 men, and there were a total of 150 that eventually boarded. (The Gaspee's sentinel, Bartholomew Cheever, estimated "about 200.")  Granted that the testimony at the court martial would have emphasized the need to surrender to a superior force.  But the fact is that on the night in question, the English felt overwhelmed, and these are the only estimates of the size of the attacking force. For such a large force, large long-boats were needed. Again, this suggests that Bowen's "largest long-boats" were easily in excess of 20 feet long.

John Mawney referred to the long-boat on which he rode as a "barge".  "Barge" was used for two types of boats associated with larger ocean going ships.  An admiral or other high ranking naval officer has on his flagship a "barge".  The barge was a large and imposing boat, and was used to carry the ranking officer to/from his command ship.  It is not the flat bottomed scow that we think of in the 21st Century.  The other 18th Century meaning of "barge" was for the large type of long-boat used to carry goods to and from a ship at anchor and the shore.  Both meanings of the "barge" term used by Mawney indicate a large vessel.  It also is consistent with his story of sitting in the stern with the boat captain and still being able to "spring forward" the length of the boat to be the first in his boat to grab a rope and get aboard the Gaspee.  Obviously, Mawney had room to move between rowers to get forward, so this was not a small boat.

Also, consider the fact that the attackers had large enough boats so that they needed only three of their boats to take the 19 English sailors of the Gaspee aboard their boats, as bound captives, and row them ashore. (19 persons, because the Master and four men had gone with a seized ship to Boston.)  Dudingston described one of the boats thus:

"During the time they were rowing me on shore, I had an opportunity of observing the boat, which appeared to me to be a very large long-boat. I saw by the man who steered her a cutlass lying by him . . . .One man, who had a little more humanity than any of the rest, said they had better land me at the Point of Pawtuxet. As I was unable to stand, they unbound five of the men and gave them a blanket to carry me up."

This description was an attempt by Dudingston to help the investigator discover the attackers' identity, and he was apparently trying to be accurate.  Dudingston was experienced in the English navy, which regularly had longboats in excess of 25 feet long on even their smaller ships.  Dudingston did not describe the boat as a pinnacle, a yawl, or any other kind of smaller rowed boat which were 15 or less feet in length.. He called it a long-boat, and did not rest on calling it a long-boat or a large long-boat. His description of "a very large long-boat" suggests that Bowen's "largest long-boats" were easily in excess of 20 feet long.

Dudingston said that he had called for Dickinson to be brought to him in the ship's cabin as Dudingston was having his wound attended to, so that Dickinson could help to identify the attackers.  Dickinson testified that he counted seven "launches and merchants ships boats" with "about one hundred and fifty" men.   (Note, Dickinson uses "launch". A "launch" was a sloop- rigged large boat , used by English warships in landing marines for amphibious warfare, a tactic King George favored. The "launch" and the "barge" were the biggest of the ship's boats carried by English warships.) Dickinson clearly wanted to tell the investigators that these 7 boats, with 150 men in them, were large long-boats, easily able to handle 20 plus men in each boat.

Left:  The re-created 16 foot longboat Genevieve used in Rhode Island re-enactments and parades is typical of boats constructed during the Revolutionary period, albeit probably much shorter than ones used to attack the Gaspee.  Right:  Typical crew dress of the time.  Click on images to enlarge.

Right:  Whaleboat currently used by the Buzzard's Bay Rowing Club that re-enacted one of the longboats that attacked the Gaspee during  the June 9, 2012 WaterFire festivities in Providence.  This boat is likely to accurately portray the size and shape of the longboats

Dudingston and Dickinson were taken ashore in different boats. Dudingston described the boat in such a manner that we can assume it easily accommodate 20 men. Dudingston was probably in Potter's boat, because the description of English sailor Patrick Earle and of Briggs agree regarding  the transport of the captain Dudingston, and because Briggs reported using his small rowboat immediately after the captain was landed. (Brigg's rowboat had been attached to, and towed by, Potter's boat after Briggs  was impressed onto Potter's boat.)

Potter's boat was described by Briggs as: "....he was in a boat which was rowing with eight oars; that the time he met the said Potter was about half an hour after he, this deponent, left the island, and he, said Potter, was about five miles from Bristol; that there were eleven men in said boat."  Briggs was impressed by the Potter group to row.  Whether Briggs was to use an additional available oar or was to give relief to the rowers,  the fact is that Potter's boat had at least four sets of oars, maybe more, was probably in excess of  28 feet, and was fully able to hold 20 men.

If Potter had a 28 foot long-boat, did Brown?  Brown had a sizable fleet of merchant ships engaged in the slave and sugar trades, and Providence was a town with a number of ships available in the harbor. Fifty whaling ships made Rhode Island their home base, bringing back spermaceti, the raw materials for Brown's candle making factory.  It is doubtful that Brown in Providence had only smaller long-boats than available to Potter in Bristol.

So, our conclusion is that Bowen's description of  "largest long-boats in the harbor" tells us of boats in excess of 25 feet in length, and most probably with 10 men rowing them (five pairs of oars).

Vice Admiral Samuel Graves, R.N., at Boston in July 1775 and under constant harassment from raiders in whaleboats — who set fire to Boston Lighthouse which is at present rendered useless and who were robbing the islands and burning the Houses and Hay thereon (which) most certainly distresses the Garrison — made a very succinct case for utilizing whaleboats: "from their Lightness and drawing little Water, they can not only out-row our Boats, but by getting into Shoal Water, and in Calms, they must constantly escape." He might have added that with a proper rig they could also sail very well.

Whaleboats were made of oaken keels with lap-strake cedar clapboards about one half-inch thick and, while extremely sturdy, were so very light that two men can conveniently carry them, though it would have taken several stout hands when the boats were loaded and the wood had made up." They were generally meant to be conveyed aboard whaling sloops and brigs and were probably about the size of Thomas Wickham's 21 Feet 8 inches Keel, which Rhode Island had taken into state service in October 1777." Double-enders, unequaled in fine lines and powerful form, were preferred by most whaleboatmen because they would back off smartly when a whale was harpooned, rather a necessity if the boat was not to be upset, were easier to build and were acknowledged by many to be more seaworthy than square-sterned boats since the gunwale amidships rises with an accelerated curve at each end, and this rise of bow and stern gives it a duck-like capacity to top the oncoming waves, so that it will dryly ride when ordinary boats would fill. These whaleboats could be rowed with four, five or six oars and will make ten miles an hour in dead chase by the oars alone."

John Brown wanted 3 Wale boats for a Brigg that's going Wailing to the Western Islands — 2 of them to be 6 ored & I of 5 ores." The Boston Newsletter (12 February 1730) spoke of a whaleboat's crew as Stersman, an Harpineer, and Four Oar Men. The five-oared whaleboat, with oars of varying lengths, was somewhat unique to North America, …. though the evidence seems to indicate that military people and privateersmen favored the six-oared boat with about nine or ten men aboard.

Long whaleboats, with twelve to sixteen oars, were also very much in vogue both as raiders and express boats. Fitted with sails and with swivels, and on occasion with a small carriage gun, perhaps a 3-pounder, the British used them to shuttle dispatches between Yorktown and New York during the military crisis in September and October 1781. …Whaleboats had been exceedingly popular in pre-Revolutionary times both as fishing boats and small coastal haulers. ...

Regarding the armed long boat Cesar, Christopher Smith, it is reasonable to surmise she was built on the English model. William Falconer defined the longboat in Universal Marine Dictionary as the largest boat that usually accompanies a ship, generally furnished with a mast and sails: those which are fitted for men of war, may be occasionally decked, armed, and equipped, for cruising short distances against merchant ships of the enemy, or smugglers, or for impressing seamen etc. Included among draughts and illustrations at the end of Falconer's text are plans for an eight-oared longboat approximately 35' long x 11' broad x 5' deep, Chapelle used a draught from the Admiralty collection in the National Maritime Museum and envisioned the typical longboat belonging to the Royal Navy, ca. 1740, as sloop-rigged" — an observation which Randle's con-temporary watercolour, View of His Majesty's Armed Vessels on Lake Champlain, October 11, 1776", tends to  confirm by portraying a longboat — then in service as an armed tender and mounting a carriage gun — rigged as a topsail sloop." According to her bond, 8 August 1778, Cesar carried two swivels and twelve men and was owned by Samuel Aborn, a Warwick merchant who had helped to outfit the 60-ton schooner Eagle and the 80-ton sloop Batchelor as privateers in 1776.