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TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



The inner surface of this tube (that next the board) has 

 attached to it a pointer, which projects slightly over the 

 scale on the board, being raised above it just sufficiently to 

 allow it to travel freely without any danger of catching. 



Fig. 2. Measuring Apparatus. 



The outer surface is provided with a pair of pillars, forming 

 a grip for the hand, between which is a thumbscrew by means 

 of which the apparatus can be firmly clamped to the rod if 

 desired. 



