This greenery, however, is a comparatively recent development in the history of Cambridge, most of it dating no further back than the latter half of the seventeenth century. In the last decade of that century an artist named David Logan (or Loggan), said to have been of Danish nationality but Scotch extraction, made a series of views of the various Cambridge Colleges, elaborated with extraordinary care and fidelity. So truthful and observant was he that a mysterious bird, long a puzzle in his drawing of the great court of Trinity, has lately been discovered, by reference to the College muniments, to have been a tame eagle then kept by the Society. His views were reissued in 1905 by Mr. J. W. Clark, the greatest living authority on Cambridge antiquities, and should be consulted by all who are interested in the development of Cambridge. In these views the existing avenues in the College enclosures at the "Backs" may be observed, but all of young trees quite recently planted (as indeed we know to have been the case from the College records), while right up to these enclosures run open treeless fields, not meadows, but corn-land, where harvesters may be seen at work and sheep grazing upon the fallow land. Most of the now green Commons are in like manner shown to have been then under the plough. The late Professor Maitland, whose recent death has been so irreparable a loss to Cambridge and to the whole historical side of English education, has shown (in his _Township and Borough_) how truly these views of Logan's represent the seventeenth century facts, and how, somewhat earlier, the arable fields had come even to the river bank on the west of the town; or, to use his own more accurate language, that the western fields of Cambridge extended to the river bank. Every old English town and village, it must be remembered, was in theory (and originally in practice) self-supporting, and contained within its boundary sufficient arable and pasture land to feed its own inhabitants and their cattle. These were known as the "Common Fields" of the place. They were not "Commons" in our modern sense of the word, but were divided into small holdings amongst the townsmen, each man's holding consisting of so many tiny strips, never more than an acre in extent, scattered as widely as possible to make things fair for all. They were cultivated upon the three course system; every landholder having the right to pasture a proportionate number of cattle on the fallow of the year, as well as in the Common Meadows. The Common Fields of Cambridge comprised about five square miles, with the inhabited part of the township nearly in the centre, and roughly coincided with the existing Parliamentary Borough, though somewhat more extensive.