The second advantage of a pointed arch is structural. The horizontal
thrust of an arch or dome varies inversely with its rise, and since a pointed
arch rises higher than a rounded one it naturally generates less thrust. In fact, the architects at the Cathedral of Milan believed that pointed arches produced no horizontal thrust whatsoever. They were mistaken, of
course, though a quinto acuto arch does generate as much as 50 per cent
less radial thrust than a shallower, semicircular one. It therefore
requires less abutment and has a lower tendency to crack or burst at its
base.