The cavalry camp is thus something like a street running down from the middle of the tribunes' tents and at right angles to the line along which these tents are placed and to the space in front of them, the whole system of viae being in fact like a number of streets, as either companies of infantry or troops of horse are encamped facing each other all along each. Behind the cavalry, then, they place the triarii of both legions in a similar arrangement, a company next each troop, but with no space between, and facing in the contrary direction to the cavalry.
They make the depth of each company half its length, because as a rule the triarii number only half the strength of the other classes.
So that the maniples being often of unequal strength, the length of the encampments is always the same owing to the difference in depth.
Next at a distance of 50 feet on each side they place the principes facing the triarii, and as they are turned towards the intervening space, two more streets are formed, both starting from the same base as that of the cavalry, i.e. the hundred-foot space in front of the tribunes' tents, and both issuing on the side of the camp which is opposite to the tribunes' tents and which we decided to call the front of the whole.
After the principes, and again back to back against them, with no interval they encamp the hastati.
As each class by virtue of the original division consists of ten maniples, the streets are all equal in length, and they all break off on the front side of the camp in a straight line, the last maniples being here so placed as to face to the front.
Walbank Commentary