In Classical architecture shafts of columns have a greater diameter at the bottom than at the top: the diminution does not result in slightly battered straight inclining slides, but a subtly convex curved swelling called entasis. In the Greek Doric Order from Paestum the shafts are much smaller at the tops than the bases, and the entasis is very obvious. Entasis can also be found on walls, spires, and towers. Entasis may have been noticed first by Allason in c.1814, but it was subsequently confirmed by C. R. Cockerell and Haller von Hallerstein. Allason published a paper in the Quarterly Journal of Science and Arts (1821) on the subject (but was indebted to Cockerell for material), and F. C. Penrose followed with detailed discussions in the 1850s.