It will be seen at once that it presents almost the features of a spiders web. A great part of the township at that date, probably nearly the whole of it in earlier times, was divided up into little narrow strips. «Divided into strips or seliones, _i.e._ acres, by balks.» «Form of the acre.» These strips, common to open fields all over England, were separated from each other not by hedges, but by green balks of unploughed turf, and are of great historical interest. They vary more or less in size even in the same fields, as in the examples given on the map of a portion of the Hitchin Purwell field. There are 'long' strips and 'short' strips. But taking them generally, and comparing them with the statute acre of the scale at the corner of the map, it will be seen at once that the normal strip is roughly identical with it. The length of the statute acre of the scale is a furlong of 40 rods or poles. It is 4 rods in width. Now 40 rods in length and 1 rod in width make 40 square rods, or a _rood_; and thus, as there are 4 rods in breadth, the acre of the scale with which the normal strips coincide is an _acre_ made up of 4 roods lying side by side. Thus the strips are in fact roughly cut 'acres,' of the proper shape for ploughing. For the furlong is the 'furrow long,' _i.e._ the length of the drive of the plough before it is turned; and that this by long custom was fixed at 40 rods, is shown by the use of the Latin word '_quarentena_' for furlong. The word 'rood' naturally corresponds with as many furrows in the ploughing as are contained in the breadth of one rod. And four of these roods lying side by side made [p003] the acre strip in the open fields, and still make up the statute acre. [Illustration: PART OF PURWELL FIELD, HITCHIN.] «Very ancient.» This form of the acre is very ancient. Six hundred years ago, in the earliest English law fixing the size of the statute acre (33 Ed. I.), it is declared that '40 perches in length and 4 in breadth make an acre.'[2] And further, we shall find that more than a thousand years ago in Bavaria the shape of the strip in the open fields for ploughing was also 40 rods in length and 4 rods in width, but the rod was in that case the Greek and Roman rod of 10 ft. instead of the English rod of 16½ ft. «Half-acres.» But to return to the English strips. In many places the open fields were formerly divided into half-acre strips, which were called 'half-acres.' That is to say, a turf balk separated every two rods or roods in the ploughing, the length of the furrow remaining the same. The strips in the open fields are generally known by country folk as 'balks,' and the Latin word used in terriers and cartularies for the strip is generally '_selio_,' corresponding with the French word '_sillon_,' (meaning furrow). In Scotland and Ireland the same strips generally are known as 'rigs,' and the open field system is known accordingly as the 'run-rig' system.