Cæsar’s camp on Greenfield common is forty paces broad, sixty long. Here he received the ambassadors of the _Trinobantes_, desiring their prince Mandubrace to be restored: they bring forty hostages and bread-corn for the army. For their reception another camp is made around this, which is 80 paces broad, 100 long. Another day came in ambassadors from the _Cenimani_, _Segontiaci_, _Ancalites_, _Bibroci_, and _Cassii_. This obliged the camp-master to add the appendix to the camps, which was of the breadth of 100 paces, equal to the length of the last; 130 in length, stretching out to the east: but in the ground-plot of that camp we see an egregious proof of my position, that they went by paces in marking out their camps; and sometimes by guess-work, in the square; which obliged the camp-master to carry his 130 paces beyond the angle of the former camp. Concerning the method of adding new occasional works to a former camp, we observe a like instance in that camp of Chlorus’s between Clarendon palace and Old Sarum; made, we may well presume, on the states of Britain sending their ambassadors hither to him, with submission to his government after the destruction of Allectus. Cæsar’s camp on Hounslow heath is very perfect, sixty paces square. His camp at Kingsbury is thirty paces broad, and forty in length. Come we now to our work at Pancras. The _prætorium_ is forty paces broad from east to west, fifty paces long from north to south: the _prætorium_ of Mandubrace is thirty paces long from east to west, forty from north to south: thereby it accommodated itself to that part of the camp, that was called _retentura_. The breadth of the whole camp was 400 paces, not reckoning the valley of the brook: the length of the whole is 500 paces. Examine the intermediate parts, they fall into whole numbers: the breadth of the pasture, comprehending the station of the _Hastati_ and _Triarii_, on the west side of the camp, is 150 paces: that of the horse is forty broad: the correspondent, or eastern part of the camp, is likewise 150 paces broad, comprehending the station of the _Triarii_ and _Hastati_; so that, subducting the space of the valley where the brook runs, the whole breadth of the camp, where the tents are pitched, contains 340 paces: a space beyond, on each side, of thirty paces wide, is supposed to be left between the tents and the _vallum_, where a camp is fortified: and then the camp contains just 400 paces broad. The camp is in length 500 paces: the thirty paces beyond, for the way between the tents and _vallum_, (where a _vallum_ is made) amounts to 560; so that the proportion of length to breadth is as 3 to 2; where strength and convenience is well adjusted, and is often the proportion of Roman cities. This space of ground was sufficient for Cæsar’s army, according to Roman discipline; for, if he had 40,000 men, a third part of them were upon guard.