Welding welding was invented in 1893, and around that time another process, oxyfuel welding, became well established. Acetylene was discovered in 1836 by Edmund Davy, but its use was not practical in welding until about 1900, when a suitable torch was developed. At first, oxyfuel welding was one of the more popular welding methods due to its portability and relatively low cost. As the 20th century progressed, however, it fell out of favor for industrial applications. It was largely replaced with arc welding, as advances in metal coverings (known as flux) were made. Flux covering the electrode primarily shields the base
Discovered attack Discovered attack In chess, a discovered attack is an attack revealed when one piece moves out of the way of another. Discovered attacks can be extremely powerful, as the piece moved can make a threat independently of the piece it reveals. Like many chess tactics, they succeed because the opponent is unable to meet two threats at once. While typically the consequence of a discovered attack is the gain of , they do not have to do this to be effective; the tactic can be used merely to gain a tempo. If the discovered attack is a check, it is