For many centuries it was common to designate cannon caliber by the weight of the projectile. So we hear of a "12-pounder" or a "32-pounder," which tells us that the gun fired a round of approximately the indicated weight. Now that sounds reasonable, until one recalls that it was rare for the word "pound" to mean the same thing in two different countries.
Comparative Weight of the Pound
Country English Ounces
Austria 15.9
Bavaria 19.75
Denmark 17.64
France 17.33
Greece 16.96
Hanover 16.50
Hansa Towns 17.09
Hesse 17.12
Naples 12.00
Netherlands 17.44
Papal States 11.96
Piedmont 11.70
Portugal 16.19
Russia 14.56
Saxony 16.49
Sicily 11.20
Spain 16.20
Sweden 15.00
Venice 16.80
To give some idea of the differences, consider the comparative weight in English measure of the 24 pounder cannon ball of each of the principal naval powers in the period 1790-1815:
Denmark 26 pounds 7.75 ounces
France 25 14.50
Netherlands 26 2.25
Russia 21 10.50
Spain 24 5.50
Sweden 22 7.75
Surprisingly, it's a rare historian who takes into account the differences in weight between the apparently identical gun poundage of opposing forces, which could reach significant proportions when dealing which major warships such as frigates (carrying anywhere from 28 to 44 guns) or ships-of-the-line (with 64 to 120 guns). In fact, for the age of sail, only William M. James (1780-1827), author of the six volume A Naval History of Great Britain: During the French Revolutionary and Napoleonic Wars, Vol. 1: 1793-1796 addressed the question directly. When preparing accounts of engagements, James carefully converted gun weights into English measure to more accurately reflect comparative firepower.
"These things must be done delicately-- or you hurt the spell." - The Wicked Witch of the West.
"We've got the torpedo damage temporarily shored up, the fires out and soon will have the ship back on an even keel. But I would suggest, sir, that if you have to take any more torpedoes, you take 'em on the starboard side." Pops Healy, DCA USS Lexington.