are then plunged into the water, and the plate (b) applied to 

 the mouth of the jai-, and that and the plate (a) being mode- 

 rately pressed against the mouth, so that they shall not slip, 

 or sufter any gas to escape, the jar, together with the plates, 

 is lifted out of the water, and set with the mouth turned 

 up. In this position the jar is ready for yielding the gas 

 to the jar into which it is to be transferred. This last jar 

 is now to be filled with water, taking care not to teave 

 any air in it, and its mouth is to be closed by the third 

 plate. It is then to be turned with its mouth downwards, 

 and, together with the third plate on which it stands, is 

 to be placed on that part of the under plate which is 

 not covered by the upper plate. The edges of the third 

 and upper plate are placed as nearly as possible in con- 

 tact; and across them the small jar, filled with Avater, is 

 to be slided till it rests entirely on the upper plate. The 

 hole in the upper plate is to be filled with a few drops 

 of water, and the jar is to be slided so as to stand over it. 

 The upper plate, and the jar standing upon it, are then to 

 be so moved over the under plate, that the holes in each 

 shall coincide. The water in the upper jar, as soon as the 

 communication is thus opened, Avill descend into the lower 

 or magazine jar, and be supplied with an equal bulk of 

 gas from below at pleasure. When a sufficient quantity 

 is transferred thus into the upper jar, it is pushed, to- 

 gether with its plate, in such a manner that the holes shall 

 no longer coincide, and, consequently, the communication 

 shall be cut off. The upper jar is slided back upon the third 



plate. 



