[15] Pedro de Ayala, writing to Ferdinand and Isabella in July, 1498 (_Spanish Calendar_, i. 210), divides the revenue of James IV into six main heads--(1) Leases of Crown lands, held for three years and redeemable by a fine. (2) Customs. "The import duties are insignificant, but the exports yield a considerable sum of money, because there are three principal articles of export, that is to say, wood, hides, and fish." (3) The profits of justice. James's predecessors "farmed it to certain persons called justices.... This king does not like to farm the administration of the law, because justice is not well administered in that way." (4) The ordinary feudal incidents--reliefs, wardships, and marriage. (5) Vacant bishoprics, abbacies, &c. (6) Rent in kind, from meat and poultry, and especially from fisheries. Only one of these, namely, customs duties, could have been regulated by the Estates, and there is on record no instance of any attempt to do so. The revenue was collected on the English system, described in the _Dialogus de Scaccario_. The sheriffs and the king's stewards collected the sums due in the counties, and the bailiffs and "custumars" had charge of the amercement of the burghs and the collection of the customs. The main differences between the system in Scotland under James IV and that of England under Henry VII is that the Scottish Exchequer Court was not so fully organized as the English, and that the system of checks on the honesty of the sheriffs, &c., was much less elaborate. All the sources of revenue were, as a rule, "farmed out"; the king received a composition, and the actual collector made as much profit as he could. [16] Gilbert Stuart, _Of the Public Law and Constitution of Scotland_, note xxviii. [17] Hill Burton, _History of Scotland_, ii. 82.