242 Proceedings of the Eoyal Society of Edinburgh. [sess. 
ments exhibited did not have the ring, which was fitted the next 
day. 
An arrangement was also exhibited by which tubes, such as 
those used by Professor Pettersson in the collection of samples of 
water for the determination of their gaseous contents, can be 
attached to the connecting-rod, and the finely drawn cut end be 
broken off by the motion of the lever in shutting the stop-cocks. 
The differential motion of the connecting-rod and the water-bottle 
(which may be replaced by another rod) affords the means of easily 
performing a number of simple laboratory manipulations in the 
deep sea ; for instance, collecting samples of water over mercury. 
In water of any considerable depth, exhausted tubes, such as Pet- 
tersson used in Scandinavian waters, would be almost certain to 
collapse, if not by the pressure alone, by the pressure assisted by 
the momentary disturbance of structural equilibrium produced by 
the sudden breaking of the point. In order to collect water in 
glass tubes at great depths, recourse must be had to the method by 
displacement of mercury, which is easily effected by means of the 
differential motion deep-sea frame. The parallel motion gas bracket, 
manufactured by Messrs Milne, and much used in drawing offices, 
supplies a frame of the kind almost ready for attachment to the 
sounding line. 
