32 Proceedings of the Royal Irish Academy. 



the U -tube X ; and it is easy to arrange that the sand in each limb 

 shall be alternately uncovered and exposed to the air when the supply 

 of solvent from the attached flask fails. It is necessary for safety to 

 take the tube B about 60 centimetres or thereabouts above the Wolf's 

 bottle. 



"Where the siphon opens within the bottle a peculiar arrangement 

 is adopted, absolutely essential to the success of the apparatus. This 

 consists in forming the lower part, t, of the siphon of soft-rubber 

 tubing, carrying at its lower end an open thistle funnel, B. The 

 object of this is to obviate a well-known difficulty in the cup-of- 

 Tan talus arrangements: viz. the failure of the siphon to "break" 

 at end of its discharge and the consequent formation of a chain of 

 gas-bubbles and water-bubbles, carrying off the water at the same 

 rate as that at which it enters the bottle. IN'ow the action of the 

 thistle funnel and rubber tube is as follows : — as the water sinks in 

 the bottle and at last begins to uncover the thistle funnel, the weight 

 of the water in this funnel elongates the rubber tube a little, so that 

 finally, when the lower lip of the funnel uncovers and the water 

 spills out of it, the contraction of the rubber tube jerks the funnel 

 completely out of the water beneath and lets the whole siphon fill 

 with air. 



This arrangement gave no trouble and worked with no more 

 attention than that required to re-moisten the gravel contained in the 

 damping tubes T. I may poiat out that the adjustment of the 

 eifective capacity of the Wolf's bottle is simply carried out by an 

 adjustment of the length of the arm of the siphon within the 

 bottle, that is, by adjusting the length of the rubber tube t. 



