A Re-Estimation of the Cargo Capacity of the Irish Rover

An independent estimate of the cargo capacity of an exceptionally ambitious sailing ship

The Irish Rover sailed from Cork in 1806 carrying bricks for New York’s City Hall. That part of the story is at least chronologically plausible: the building was under construction from 1803 to 1812. Whether anyone ordered Irish bricks is another question. New York City’s construction history

The trouble begins with the rest of the cargo.

The song’s manifest includes a million bales of rags, two million barrels of stones, three million sides of horsehide, four million barrels of bones, five million hogs, six million dogs, seven million barrels of porter, and eight million bales of goats’ tails.

Twenty-seven masts suddenly sound less like an extravagance and more like an opening bid.

But how much ship would this actually require?

Establishing the units of absurdity

A manifest with precise quantities is helpful. A manifest with precise quantities and no package dimensions is less helpful.

There is no universal bale. A barrel’s liquid capacity is smaller than the space it occupies aboard ship. Dogs come in inconveniently different sizes. The song also declines to explain whether its eleven million animals require dinner.

To make the arithmetic possible, I will use the following assumptions. These are modeling choices, not recovered specifications from a Cork shipping office.

Bales: Each bale measures half a meter on every side, giving a volume of 0.125 cubic meters, or 125 liters. This applies equally to the rags and tails.

Barrels: Each holds approximately 164 liters, using the modern British brewing barrel as a convenient reference. The brewing industry lists that unit at about 163.6 liters. This is a benchmark, not a claim about the exact containers used in 1806. British Beer & Pub Association container guidance

Allowing for the barrel itself, I assign each an external envelope of 0.20 cubic meters. I then assume those envelopes occupy 80 percent of their allotted hold space. Each barrel therefore requires:

0.20 ÷ 0.80 = 0.25 cubic meters of hold.

Horsehides: Each “side” is half a hide. I assign it one square meter of area and four millimeters of compressed thickness. Adding a packing allowance gives 0.005 cubic meters, or five liters, per side.

Hogs and dogs: I treat these as preserved carcasses, assigning 125 liters per hog and 30 liters per dog, including modest packing space. These are deliberately simple averages. A live-animal interpretation would require a separate calculation for pens, ventilation, feed, water, and the crew’s rapidly deteriorating morale.

Adding the cargo

With those assumptions, the manifest becomes:

CargoQuantityHold space per unitTotal hold spaceBales of rags1,000,0000.125 m³¹²⁵,000 m³Barrels of stones2,000,0000.250 m³⁵⁰⁰,000 m³Sides of horsehide3,000,0000.005 m³¹⁵,000 m³Barrels of bones4,000,0000.250 m³¹,000,000 m³Hogs5,000,0000.125 m³⁶²⁵,000 m³Dogs6,000,0000.030 m³¹⁸⁰,000 m³Barrels of porter7,000,0000.250 m³¹,750,000 m³Bales of goats’ tails8,000,0000.125 m³¹,000,000 m³Total

5,195,000 m³

The result is approximately 5.2 billion liters of cargo space, before adding a single brick.

The porter alone occupies roughly a third of the total. Whatever else went wrong aboard the Irish Rover, inadequate provision of beer was apparently not among its shortcomings.

A small correction with three zeroes attached

The earlier examination of this question contains a unit error worth correcting.

Its assumed horsehide side measures ten square feet and half an inch thick. Multiplying those dimensions gives approximately 0.0118 cubic meters, which equals 11.8 liters, rather than 0.0118 liters.

Across three million sides, those dimensions imply about 35,400 cubic meters of hide before allowing for packing.

My estimate uses thinner compressed hides and arrives at 15,000 cubic meters. Either way, the hides are a comparatively small item. Correcting them does little to resolve the seven million barrels of porter.

The ship also has to float

Volume is only half the problem. The stones and beer deserve a weight calculation.

At 164 liters per barrel, the porter amounts to:

7,000,000 × 164 = 1,148,000,000 liters.

Approximating its density as one kilogram per liter gives 1,148,000 metric tonnes of beer, excluding the barrels.

For the stones, assume a bulk density of 1,600 kilograms per cubic meter. This is an illustrative allowance for loose stone with spaces between the pieces, rather than solid rock.

2,000,000 × 0.164 × 1,600 = 524,800,000 kilograms.

That is another 524,800 tonnes.

Together, the beer and stones weigh approximately 1.67 million tonnes. We have yet to weigh the bones, hides, animals, bales, containers, bricks, provisions, or ship.

The vessel would need to displace enough water to support all of that. A sufficiently large warehouse is not automatically a sufficiently buoyant boat.

What would it look like?

Suppose usable cargo space occupies 65 percent of the vessel’s enclosed volume. The remainder accommodates structure, crew spaces, access, equipment, and other necessities.

Our cargo then implies:

5,195,000 ÷ 0.65 ≈ 8,000,000 cubic meters of enclosed volume.

For a sense of scale, a rectangular box 800 meters long, 100 meters wide, and 100 meters high encloses eight million cubic meters.

That is a volume comparison, not a seaworthy design. A real hull has shaped ends, structural constraints, and a waterline that cannot be selected by optimism. Still, it establishes the general neighborhood: the Irish Rover is beginning to resemble a waterfront district with sails.

How much confidence should we place in this?

The arithmetic is straightforward. The packaging is speculative.

The nine million bales are especially influential. If each occupies 50 liters instead of 125, the total falls to approximately 4.52 million cubic meters. At 250 liters per bale, it rises to 6.32 million cubic meters.

That range changes only the bale assumption. Different barrels, animal sizes, preservation methods, and packing arrangements could move the result further.

The defensible conclusion is therefore an order of magnitude: several million cubic meters of cargo space, with a central estimate of about 5.2 million, under the assumptions used here.

And still no bricks.

The song eventually supplies fog, disease, and a rock to explain the ship’s loss. The cargo manifest suggests that the first serious difficulty would have been persuading Cork to launch it.