The Tithe Commutation maps and awards afford the richest mine of information for the period since 1836. We have seen that according to the analysis of them published by the Copyhold, Enclosure and Tithe Commission in 1873, they indicated the existence at that date of 264,307 acres of common fields. We have already seen how untrustworthy this estimate is if taken for a basis for calculating the area of existing common fields, how inaccurate it was even at the date at which it was published. But one great source of inaccuracy in it, as we have seen, is the assumption that no enclosure, other than by Act of Parliament, took place after the date of Tithe Commutation. If we could eliminate all other errors, and also get a perfectly accurate statement of the area of existing common fields, we should then know how much enclosure of common fields has taken place without Parliamentary intervention since the date of Tithe Commutation. This date, of course, is different in different parishes, but the average date is about 1845. To eliminate all other errors it would be necessary to go over all the work again, a task which would take a single investigator several years of continual labour, and would not then be accomplished unless the investigator were himself infallible. We must therefore be content with an approximate correction.[92] [92] There are no less than 11,783 separate sets of awards and apportionments, each with its map. The maps vary in size from about six or seven to over a hundred square feet each. The apportionments are bulky rolls of parchment. The tithe maps and awards deposited with the Tithe Commission cover about three-quarters of the area of England and Wales. The amount of common field in the other quarter is estimated on the assumption that in each county the part for which there are no tithe awards in the custody of the Tithe Commission contained the same proportion of common field as the part for which title awards existed. The common fields thus estimated amount to about two-fifths of the total estimate. If the particulars given in the return for the different counties were added up, we should get the statement:-- Common Field Lands. Acres. Areas ascertained from the tithe documents 163,823 Estimated additional areas 100,484 ─────── 264,307 ═══════ We have seen that assuming the total of 163,823 acres is correctly “ascertained,” the estimate of 100,484 acres for the other parishes is very excessive, because the most frequent reason for no title documents existing in the custody of the Tithe Commission is that the commutation of tithes was effected before 1836 by a local Enclosure Act, which swept away the common fields.