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. [Illustration: 105. Arches in the Pyramids at Meroë. (From Hoskins.)] This has been felt by the architects of all ages and in all countries: still, the advantage of being able to cover large spaces with small stones or bricks is so great, that many have been willing to run the risk; and all the ingenuity of the Gothic architects of the Middle Ages was applied to overcoming the difficulty. But even the best of their buildings are unstable from this cause, and require constant care and attention to keep them from falling. The Indian architects have fallen into the other extreme, refusing to use the arch under any circumstances, and preferring the smallest dimensions and the most crowded interiors, to adopting what they consider so destructive an expedient. As mentioned in the Introduction (page 22), their theory is that “an arch never sleeps,” and is constantly tending to tear a building to pieces: and, where aided by earthquakes and the roots of trees, there is only too much truth in their belief. The Egyptians seem to have followed a middle course, using arches either in tombs, where the rock formed an immovable abutment; or in pyramids and buildings, where the mass immensely overpowered the thrust; or underground, where the superincumbent earth prevented movement.