A mixed jet can be used for oxygen and coal gas, and the light w-ould be about the same as a blow-through jet with the same gases. The hydrogen should be rather more than 2 to 1 of oxygen, and the best proportion is being used when the best light is obtained. With coal gas and oxygen, use about 10 of gas to 8 of oxygen: here, again, turn on the oxygen till the best light results. If oxygen cannot be obtained at a definite pressure from a bag, fill a bag with coal gas also, and leave both in a double set of pressure boards under the same pressure. Failing this, the pressure of oxygen will commence at 9 in., and will gradually fall to nothing. With an oxygen cylinder the pressure can be regulated to about that of the gas. For preparing oxygen. 2 parts of chlorate to 1 part of oxide of manganese are heated in a retort. Wright recommends 21b. of chlorate to 1/2 lb. oxide of manganese and 6 oz. of common salt, because the oxygen comes off from this mixture very regularly, llb. of the first mixture yields about 4,800cub. in. of oxygen, and lib. of the second mixture yields about 5,000cub. in.

To compress the mixture, powder and moisten it with water first.