found to answer well, and conceive may be admitted as 

 a useful instrument into a philosophical laboratory. 



The principal part of this apparatus consists of two pieces 

 of plate glass, with a hole of about half an inch diameter 

 drilled through each. They should be something broader, 

 and about twice as long, as the diameter of the jars used 

 in collecting and transferring the gasses. The holes should 

 be disposed as in the figure. That in the plate (Fig. 1.), 

 marked («), should be nearly in the middle of the piece. 

 The hole in the upper plate (b), near the extreme edge. 

 The upper plate is shorter than the under plate, and its 

 edge is ground fair and straight, so as to fit the edge of 

 the third plate, which is not drilled, and should be a square 

 piece cut off the second plate, as it is very necessai'y that 

 these two plates should be of the same thickness. The 

 length of these plates together should exceed that of the 

 under plate about an inch. It is rather better to grind 

 the polish off the plates with a little fine emery, as they 

 slide more equably over each other Avhen so prepared. 

 All the jars to be used with them should have their mouths 

 ground on a flat plate with fine emery. Things being 

 thus prepared, the transferring plates may be used in the 

 following manner, particularly when the jars for collecting 

 the gasses are large. 



When the jars, inverted in the usual manner in the 

 pneumatic trough, are filled with the gas in any propor- 

 tion, the two plates (« and b) are laid over each other in 

 such a situation, that their holes shall not coincide; they 



are 



