First, the extinguisher valve is removed and the threads and interior of the cylinder are checked for corrosion, pitting, and any other abnormalities. [29 CFR 1910.157(f)(3)] If the cylinder passes the visual inspection, it is placed into a steel chamber, which is then filled with water at normal pressure.
Updated April 17, 2017. The earliest dated printed book known is the Diamond Sutra, printed in China in 868 CE. However, it is suspected that book printing may have occurred long before this date. In 1041, movable clay type was first invented in China.
Three hundred years ago on 24 April 1704, John Campbell, the postmaster of Boston, published the first issue of the Boston News-Letter. A small single sheet, printed on both sides, the News-Letter made history as the first continuously published newspaper in America. The Boston News-Letter appeared weekly until 1776 and had no competition in Boston until 21 December 1719, when the first issue of the Boston Gazette appeared.