— [154], last line, for “tubular,” read “tabular.”
— [156], l. 4 from bottom, for “washer band,” read “washer used.”
— [164], l. 10 to 14, inclusive. The first number of ratios should be 20 instead of 15.
— [166], l. 11, for “69 B,” read “69 A.”
— [171], head of col. 5 of table, for “Rod of Arch,” read “Rad. of Arch.”
— [173], l. 25, for “ability,” read “stability.”
— [173], l. 32, for “Whence,” read “Where.”
— [175], l. 8, for “triangular,” read “diagonal.”
— [178], l. 3, for “article,” read “outside.”
— [184], l. 4 from bottom, for “barriers,” read “voussoirs.”