'55 



th March, 1892. 



John H. MacIlwaine, read a Paper on 

 THE TONNAGE OF SHIPS. 



Mr. MacIlwaine said — The word " Tonnage," as applied to 

 ships, originally meant an estimate or measure of the ship's 

 carrying capacity. 



The term " Tons Burthen " is probably the oldest expression 

 for what we now call " Tonnage." It was used to mean an 

 estimate of either the dead-weight carried or the internal 

 capacity of the ship ; and in the type of vessel in use at the 

 beginning of this century it generally approximated to both, 

 calculating the internal capacity at 42 cubic feet to the ton. 



This term " Tons Burthen," and also the word " Tonnage," 

 are supposed to be derived from the French custom of estimating 

 the rating of a ship from the number of tuns of wine she could 

 stow and carry, reckoning four casks to the tun. 



Now, the word " Tonnage " has two separate, and generally 

 very different, meanings. 



First, it may be used to express the real capacity of the ship 

 for carrying cargo ; this I would call the " Actual Tonnage," 

 and it pretty fairly represents the earning power of the vessel. 



Second, the term " Tonnage " may be used to express the 

 *' Nominal Tonnage " on which a vessel pays dues, now called 

 the " Nett Register Tonnage." 



The actual tonnage is obviously the most important from an 

 owner's point of view, and also most interesting to the naval 

 architect, for on it the amount of freight earned will chiefly 

 depend ; still, nett register tonnage is in some cases an equally 

 important element in the earning power of a vessel. 



It is so obvious as to be hardly worth mentioning, that in all 



