Note 459 — Chapter XV
Reading edition
Among other advantages the projectors offer an almost absolute safety of boilers from explosion, as they are made of 3-inch wrought-iron tubes ⅜ inch thick; the boilers when put together are proved to 2500 lbs. hydraulic pressure on the square inch, are worked from 300 lbs. to 500 lbs. per square inch as desired, and their bursting pressure is 20,000 lbs. per square inch.