176

curved line CB, before obtained, will per-haps, strictly speaking, pass through thecentre of gravity of each lamina eM of thematter; but assume the line to be in themiddle of its thickness, then its extradosand intrados will be distant from it everywhere, as the secant of the angle made bythis curve with a horizontal line. For ex-ample, if the extrados and intrados be each

E c

distant from C=--, then the extrados and

E Ttl

intrados will be each distant from B=—

assuming the form shown by the dottedlines.