1876.] of Coal-dust in Colliery Explosions. 363 



cylinder (fig. 5) is 2 feet long by 8 inches in diameter ; it has a cock (e and/) 

 at each end, a water-gauge at the side, and a scale, each division of 



which represents one volume of the measuring-cylinder. In the interior 

 it is divided into three compartments by two diaphragms (g and h) ; these 

 compartments communicate with each other through ten |-inch holes 

 (o o) in each diaphragm, ranged in a circle whose centre is the axis of 

 the cylinder. Tig. 6 represents the essential parts of the lamp appa- 

 ratus in section. It consists of a wick-holder and an oil vessel, above 

 which there is a chamber b, with a branch pipe (a) on one side and a 

 circular opening (o o) on the top. This is surmounted by a glass chimney 

 (d) covered on the top with a piece of tin-plate (c), in which there is a 

 |-inch round hole (d). The water-bucket is of the same capacity as the 

 mixing-cylinder, and has a cock on one side at the bottom. The india- 

 rubber tubes are used for the purpose of connecting the cylinders with 

 each other, with the water-bucket, &c. Each cylinder can be filled with 

 water or emptied, as may be required, by connecting the cock at its lower 

 end with the one in the water-bucket, and placing it below or above the 

 level of the water in that vessel after the cocks have been opened. 



Both cylinders are filled with water in the first place : the water in 

 the larger one is then allowed to flow out, the cock at its upper end 

 being open to the atmosphere, until it contains any desired number of 

 volumes of air, each volume equal to the capacity of the smaller cylinder. 



The cock at the top of the smaller cylinder is connected with the gas- 

 pipe ; the branch cock c is opened, and firedamp allowed to pass through 

 it so as to expel the air from the india-rubber tube ; the jet of gas is 

 ignited and kept burning, while the water is permitted to flow out at 

 b until the required volume of gas is obtained : all the cocks are then 

 closed. 



The two cylinders are now connected together at both top and bottom, 

 care being taken that the upper connecting-tube is filled with firedamp 

 and the lower one with water when the connexion is made ; the four 

 cocks are opened, and the small cylinder is so placed that its top is just 

 below the level of the water in the other. The gas is thus quickly trans- 



2"e2 



