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VII. 



AN APPARATUS FOR SEPARATING THE MINERAL CON- 

 STITUENTS OP ROCKS. By W. F. SMEETH (Peno- 

 logical Laboratory, Trinity College, Dublin). 



i 

 [Communicated by Professor Sollas.] 



[Read February 14, 1S88.] 



There are several weighty objections to the apparatus which is 

 at present employed for separating the mineral constituents of 

 rocks. Briefly, it consists of a funnel-shaped vessel, the stem of 

 which is considerably prolonged, and is capable of being closed at 

 various points of its length by glass stopcocks. These stopcocks 

 offer the first objection. They are difficult to make, and cannot 

 have a bore greater than from two to three millimetres in diameter ; 

 consequently there is more or less hindrance to the passage of the 

 mineral particles up and down the tube. Again, the liquid, when 

 poured in above, will not pass these narrow apertures, owing to 

 the air in the lower part of the tube. This involves passing a 

 capillary stirring-rod down to pump out the air ; and there is 

 always the risk of this rod breaking in the tube, which would 

 necessitate emptying everything out and starting afresh. Lastly, 

 the vessel will not stand of itself, but must be supported. The 

 piece of apparatus to be described claims to have obviated these 

 difficulties satisfactorily. 



It consists of an urn-shaped vessel v (Fig. 1), closed at the top by 

 a large stopper. The lower part of this vessel is drawn out into a 

 neck, n, which is ground so as to fit accurately into the top of the 

 bottle, b, of which the sides are vertical, and which has a projecting 

 lip, I. The bottle is attached to a glass foot, which forms a firm 

 support for the whole. The essentially new feature in the 

 apparatus is the stopper, s (Fig. 2), with a long handle, so that it 

 can be passed through the upper opening, and completely close the 

 orifice of the neck, n. 



To make a separation, join the parts together, as shown in 



