In chapter 3 of book 1, Smith touches on the enormous cost advantage of sea transport over land transport in the 18th century. He doesn't compare prices directly, but he breaks down the labor input:
- A broad-wheeled waggon, attended by two men, and drawn by eight horses, in about six weeks time, carries and brings back between London and Edinburgh near four ton weight of goods.
That stopped me short. Three weeks in each direction! As the footnotes, Britain made rapid improvements in ground transportation in the subsequent decades, but still...
- In about the same time a ship navigated by six or eight men and sailing between the ports of London and Leith, frequently carries and brings back two hundred ton weight of goods.
He of course realizes that one could send two hundred tons by land transport, by sending 50 wagons. But then he reckons that in that case, instead of 6 to 8 men, you'd have 100 men and 400 horses to feed for six weeks; and notes as an aside that feeding a work horse is just as expensive as feeding the laborers.
- Whereas, upon the same quantity of goods carried by water, there is to be charged only the maintenance of six or eight men, and the wear and tear on a ship of two hundred tons burthen, together with the value of the superior risk, or the difference of the insurance between land and water-carriage.
(I'm working for memory, but as far as I can tell this is the first place where he casually mentions that increased risk must be accounted for as increased cost.)
Smith rightly concludes that at this cost, were only land travel to be available, that long-range commerce would be impossible. "Who could bear the cost of land transport between London and Calcutta?"
Cannan (the editor) quibbles a bit:
- The superiority of carriage by sea is ... probably exaggerated. [Playfair in 1805] says a waggon of the kind described could carry eight tons, but, of course, some allowance must be made for thirty years of road improvement.
But then in a later note he drops some really interesting data:
- Playfair ... says that equalizing the out and home voyages goods were carred from London to Calcutta [around 1805] at the same price (12s per cwt.) as from London to Leeds by land.
I make London to Leeds at about 200 miles, and London to Calcutta by sea (prior to the Suez Canal) as about 8,000 miles -- so this is a roughly forty-fold difference in cost per mile.
To return to chapter 3 -- these costs are cited to explain why some locations and countries developed division of labor earlier, especially focusing on the availability of easy transport.
I suspect that economic historians might treat this topic differently now (particularly in light of Marxism). However, as an example of Enlightenment practical reasoning, this chapter is delightful: an educated person reasoning and educating the reader about society much as a physicist (Feynman comes to mind) might reason and educate the reader about an interesting physical problem.
Generally speaking, one must work hard to prepare a graceful argument. We should admire chapters such as this not only for the insight they give us, but also for the skill of their construction.