So far as we can now understand from the discoveries that have been made, it seems that the Assyrians used the pointed arch for tunnels, aqueducts, and generally for underground work where they feared great superincumbent pressure on the apex, and the round arch above-ground where that was not to be dreaded; and in this they probably showed more science and discrimination than we do in such works.
104. Arch of the Cloaca Maxima, Rome. Scale 50 ft. to 1 in.
In Europe the oldest arch is probably that of Cloaca Maxima at Rome, constructed under the early kings. It is of stone in 3 rims, and shows as perfect a knowledge of the principle as any subsequent example. Its lasting uninjured to the present day proves how well the art was then understood, and, by inference, how long it must have been practised before reaching that degree of perfection.
From all this it becomes almost certain that the arch was used as early as the times of the pyramid-builders of the 4th dynasty, and was copied in the tombs of Beni-Hasan in the 12th; though it may be that the earliest existing example cannot be dated further back than the first kings of the 18th dynasty; from that time, however, there can be no doubt that it was currently used, not only in Egypt, but also in Ethiopia and Assyria.
It would, indeed, be more difficult to account for the fact of such perfect builders as the Egyptians being ignorant of the arch if such were the case; though, at the same time, it is easy to understand why they should use it so sparingly, as they did in their monumental erections.
Even in the simplest arch, that formed of only two stones, such as is frequently found in the pyramids, and over the highest chamber (Woodcut No. [8]), it will be evident that any weight placed on the apex has a tendency to lower the summit, and press the lower ends of the stones outwards. Where there was the whole mass of the pyramid to abut against, this was of no consequence, but in a slighter building it would have thrust the walls apart, and brought on inevitable ruin.
The introduction of a third stone, as in the arch (Woodcut No. [101]), hardly remedied this at all, the central stone acting like a wedge to thrust the two others apart; and even the introduction of 2 more stones, making 5, as in Woodcut No. [105], only distributed the pressure without remedying the defect; and without the most perfect masonry every additional joint was only an additional source of weakness.
105. Arches in the Pyramids at Meroë. (From Hoskins.)