Thirdly, and lastly, There is no certain criterion by which we can determine on which side what is called the balance between any two countries lies, or which of them exports to the greatest value. National prejudice and animosity, prompted always by the private interest of particular traders, are the principles which generally direct our judgment upon all questions concerning it. There are two criterions, however, which have frequently been appealed to upon such occasions, the custom-house books and the course of exchange. The custom-house books, I think, it is now generally acknowledged, are a very uncertain criterion, on account of the inaccuracy of the valuation at which the greater part of goods are rated in them. The course of exchange is, perhaps, almost equally so.