4 Gibson, Draught produced by an Inclined Rod. 



being at the level represented by the central circle in 

 each case. The three numbers in each square refer to 

 the readings taken at the centre of the square, the first 

 and second being the gauge readings respectively with 

 and without the poker in position, while the third gives 

 the ratio of the square root of these two, and therefore 

 the relative velocity of flow with and without the poker. 



Experiiiicjit I. 



Poker inclined at 50" to horizontal with its tip in the 

 plane of the frame. Blast pipe horizontal, \V below level 

 of, and 19" behind tip of poker. 



