Chap. XXIII.
1415
it can be placed in any required partof the vault. Turning scaffolds arerendered more steady when the leverwhich supports the workman iselevated at the side of a quad-rant, to which it maybe secured at the heightrequired.
Some scaf-folds are madewith a num- / .%ber of floors ;
Fig 2365.
the most simple are those suspended from holesin the vault.
The scalfold used at St. Peter’s at Rome in 1773, when the great vault was repaired andre-decorated, was of a novel and ingenious character. Itwas composed of two sets of principals united together bybraces and intermediate ties, upon which the planks for theworkmen were laid : this scaffold traversed from one end ofthe vault to the other; it was raised in one mass by ropesand pulleys, and lowered to the pavement by the same
I
Fig. 2366. scapfolo used at the dome of st. peter's.
means when the work for which it was destinedwas completed, the ropes were passed through theholes left in the vaulting for the purpose. Theeditor cannot omit the opportunity of bearing histestimony to the skill and ingenuity of the Italians in making scaffolds for the most temporary pur-poses : when engaged in taking the casts andmeasurements of various remains in the Imperialcity, the ladders and scaffolds prepared by theworkmen for his use were of the most perfect kind :although light, and apparently fragile, he oftenmounted upwards of 100 feet, and remained thewhole of the day at his work, without the slightestrisk of accident.
The scaffold for the dome of the same churchwas contrived by Pietro Albertini at the same time :the diameter of this beautiful piece of carpentrywas 133 feet, and the height nearly 80 feet: it wasformed of three frames, the vertical timbers of whichwere suspended by iron rings that passed over hooksinserted in the masonry of the vault to receivethem. When a portion of the dome was repaired4x4