Fig. 240.
Fig. 241.
[ CXXXIII]
Opening or Arched Window in a Vault
First draw the vault AEB. To introduce the window K, the upper part of which follows the form of the vault, we first decide on its width, which is mn, and its height from floor Ba. On line Ba at the side of the arch form scales aa·S, bb·S, &c. Raise the semicircular arch K, shown by a dotted line. The scale at the side will give the lengths aa·, bb·, &c., from different parts of this dotted arch to corresponding points in the curved archway or window required.
