By 1851, Yorkshire, Lancashire, the Isle of Lewis, and several counties in the south of Scotland were finished on the six inch scale.
Then began that long controversy which has been well termed the "battle of the scales" and which for eleven or twelve years retarded the progress of the survey and led to a large waste of public money.
During the time that the Ordnance Surveyors were engaged in making their six inch map of Lancashire and Yorkshire they were called upon and employed to make, at the expense of the land owners, twenty-three plans of parishes and townships on the scale of twenty-six and 2/3 inches to one mile for tithe commutation.
It was even found that the plan of London, made for the Metropolitan Commissioners of Sewers, on the scale of sixty inches or five feet to one mile was inapplicable to house drainage within the area.
Between 1851 and 1852 no fewer than three select committees and one royal commission deliberated on the scale for the survey, and fourteen blue books were presented to Parliament.
The main point of the controversy was whether the six inch or some larger scale was best fitted for the national map. A host of persons eminent in science were consulted on the subject, and a great diversity of opinion was found to exist, the weight of evidence, however, inclining by a majority of four to one, to a scale of from 20 to 262/3 inches to a mile.
In 1853 a statistical conference held at Brussels and attended by twenty-six delegates from the chief States of Europe considered the question of national maps or cadastres, and pronounced unanimously in favor of a scale of 1/2500th of nature equivalent to about 251/3 inches to a mile, recommending at the same time that the cadastre on this scale should be accompanied by a more general map on the scale of 1/10,000 equivalent to about six 1/3 inches to a mile, and thus very nearly corresponding to the six inch scale of the Ordnance Survey.
The scale finally adopted of 1/2500, on which the whole of England has at last been surveyed, is one which corresponds with that adopted for the national maps and plans of the chief countries for Europe. Lastly it possessed the incidental advantage that a square acre is to all practical intents represented on the plans by a square inch.
Among the many public purposes which the national map was expected to subserve are the following: the valuation of property for the equitable adjustment of taxation and assessment; the sale and transfer of land and the registration of title; railway and other civil engineering work, such as the construction of roads and canals, large sanitary and drainage schemes, military engineering works, hydrographical, geological and mineral surveys; the reclamation and improvement of waste lands, and of land from the sea; transactions affecting land as between landlord and tenant; statistical surveys, the setting out and adjustment of parochial and other public boundaries and so forth.
It has been amply proved on the best evidence that a map, with levels, on a scale of something like twenty-five inches to one mile is the smallest which can properly fulfill all these requirements.