THE LEANING TOWER OF PISA. [2] |
Sir John Leslie used to attribute the stability of this tower to the cohesion of the mortar it is built with being sufficient to maintain it erect, in spite of its being out of the condition required by physics—to wit, that "in order that a column shall stand, a perpendicular let fall from the centre of gravity must fall within the base." Sir John describes the column of Pisa to be in violation of this principle; but, according to designs shown to Dr. Cumming, at Pisa, in 1836, the perpendicular does fall within the base.
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