Although every tract of land was assigned for a definite object and placed under specified guardians, the _vakfs_ were a matter of public record, and the accounts of all were kept by the treasury department in the appropriate bureaus. The subjects who lived on _vakf_ lands seem to have been better treated than those on lands of other sorts, just as in the West in the Middle Ages the serfs of the church were often better off than other serfs.[639] There were three classes of _vakfs_,—the regular _vakfs_ of the mosques, the _vakfs_ for charitable purposes, and the customary _vakfs_ of the mosques. The last were chiefly in the nature of investments of the funds of the mosques, and were according to _Kanun_ rather than _Sheri_.[640] In the second class were included endowments of schools, libraries, hospitals, bridges, fountains, caravanserais, public baths, convents for dervishes, and the like. The narrow provision of the Ruling Institution for public service was in this way supplemented.[641] The first class deserves further attention. The chief material unit in connection with the Moslem Institution was the mosque. Each great mosque was a large house of worship, with a group of smaller institutions clustered about it, such as colleges, law schools, hospitals, insane asylums, and soup-kitchens. For the support of these and of all persons who conducted them, the income from the _vakfs_ of the mosque was applied. In many cases the lands which had belonged to Christian churches before the Ottoman conquest were assigned as _vakfs_ for the support of the mosques into which the churches were converted. For example, the grounds of the sultan’s principal palace had belonged to the church, and were assigned as _vakf_ to the mosque of Aya Sofia. When Mohammed II took them for his palace he pledged a revenue of one thousand and one aspers a day to the great mosque.[642] This church was one of eight in the city of Constantinople which were so treated.[643] The revenue of Aya Sofia was estimated at two hundred thousand ducats a year.[644] The income of the principal mosques being much larger than the expenses, a considerable portion of the surplus was used by the guardians for their own benefit, although they were supposed to receive no compensation, but to labor for the love of God. The fact is that many of the sultan’s _kullar_ provided an inheritance for their sons and descendants by setting apart for specific purposes lands in _vakf_, of which the desired persons should be administrators, it being clearly understood that a portion of the income should be retained by them.[645] The remainder of the surplus was held in a special treasury by the appropriate bureaus, or was reinvested in customary _vakfs_, or was lent to the government. The _vakfs_ as a whole supported all the official members of the Moslem Institution, except that the judges derived much of their income from fees and fines.[646] The treasury department