so byzantine history ended on may 29 , 1802, the outstanding russian scientist vasily petrov discoveredc arc. this is one of the forms of plasma of the fourth state of matter petrov designed a galvanic battery of 2,000 pairs, zinc and copper circles with cardboard pads soaked in ammonia for insulation went into sealing wax. the total height of the battery pillars was 12 m, due to the high power, a spark discharge or electrical breakdown occurred in the air between two carbon electrodes by means of ionization of air molecules. electric arc. petrova found application in sveta , electric welding technology and other areas. petrov had other scientific achievements, and he is considered the founder of russian electrical engineering. on may 29, 1860, pavel tretyakov, the richest manufacturer and philanthropist , made a will, according to which he left his collection of paintings and 150,000 rubles in moscow. silver for the art gallery. tretyakov was barely 30, but he had already begun to collect his collection, he considered it the main business of his life, he gave preference for the paintin