The era of the wooden steam ship-of-the-line was brief, because of new, more powerful naval guns. In the 1820s and 1830s, warships began to mount increasingly heavy guns, replacing 18- and 24-pounder guns with 32-pounders on sailing ships-of-the-line and introducing 68-pounders on steamers. Then, the first shell guns firing explosive shells were introduced following their development by the French Général Henri-Joseph Paixhans, and by the 1840s were part of the standard armament for naval powers including the French Navy, Royal Navy, Imperial Russian Navy and United States Navy. It is often held that the power of explosive shells to smash wooden hulls, as demonstrated by the Russian destruction of an Ottoman squadron at the Battle of Sinop, spelled the end of the wooden-hulled warship. The more practical threat to wooden ships was from conventional cannon firing red-hot shot, which could lodge in the hull of a wooden ship and cause a fire or ammunition explosion. Some navies even experimented with hollow shot filled with molten metal for extra incendiary power.