XL.--Having arrived at Uxellodunum, contrary to the general expectation, and perceiving that the town was surrounded by the works, and that the enemy had no possible means of retiring from the assault, and being likewise informed by the deserters that the townsmen had abundance of corn; he endeavoured to prevent their getting water. A river divided the valley below, which almost surrounded the steep craggy mountain on which Uxellodunum was built. The nature of the ground prevented his turning the current; for it ran so low down at the foot of the mountain, that no drains could be sunk deep enough to draw it off in any direction. But the descent to it was so difficult, that if we made opposition, the besieged could neither come to the river, nor retire up the precipice without hazard of their lives. Caesar, perceiving the difficulty, disposed archers and slingers, and in some places, opposite to the easiest descents, placed engines, and attempted to hinder the townsmen from getting water at the river, which obliged them afterwards to go all to one place to procure water. XLI.--Close under the walls of the town, a copious spring gushed out on that part, which for the space of nearly three hundred feet, was not surrounded by the river. Whilst every other person wished that the besieged could be debarred from this spring, Caesar alone saw that it could be effected, though not without great danger. Opposite to it he began to advance the vineae towards the mountain, and to throw up a mound, with great labour and continual skirmishing. For the townsmen ran down from the high ground, and fought without any risk, and wounded several of our men, yet they obstinately pushed on and were not deterred from moving forward the vineae, and from surmounting by their assiduity the difficulties of situation. At the same time they work mines, and move the crates and vineae to the source of the fountain. This was the only work which they could do without danger or suspicion. A mound sixty feet high was raised; on it was erected a turret of ten stories, not with the intention that it should be on a level with the wall (for that could not be effected by any works), but to rise above the top of the spring. When our engines began to play from it upon the paths that led to the fountain, and the townsmen could not go for water without danger, not only the cattle designed for food and the working cattle, but a great number of men also died of thirst.