The third stage, which was imposed in the same way upon the second, was also twenty-six feet high, and was a square of 188 feet.

Thus far the plan had been uniform and without any variety; but at this point an alteration took place.

The height of the fourth stage, instead of being twenty-six, was only fifteen feet.

In other respects however the old numbers were maintained; the fourth stage was diminished equally with the others, and was consequently a square of 146 feet.

It was emplaced upon the stage below it exactly as the former stages had been.