Velocity of Transmission of Disturbances through Sea-ivater. 531 



.„,. v Bl, - AP 



But the velocity, calculated on supposition of the firing point being in 

 line, is 



AB 



V BP-AP sm*-sin/? 



cos „ ' 



V AB sine = e 



cos - 

 2 



3*5 3" 5 



From the figure tan * = — -, tan /3 = 



. • . « = 8° 39' 9" ft = 1° 2' 20" = 7° 36' 49", 



and X, t= 0-99863 = 1-0-00137. 



Thus the true velocity V is less than the velocity calculated in the 

 General Table by 0*137 per cent, of the velocity in the Table. 



This amounts to— 



For the mean of Class A, viz , 1732 metres, the correction is 2 37 metres. 



» 1775 „ „ 243 „ 



„ C, „ 1942 „ „ 2*66 „ 



n V* n 2013 » n 2- 76 „ 



Suppose the firing point distant 1*5 metre out of line, a similar 

 calculation shows the correction to the velocity in the Table to be 

 0-00026 of that velocity or 0-026 per cent. 



For the mean velocity of Class A this correction is 0*45 metre. 



B 0-46 „ 



,, C ,, 0*50 ,, 



D „ 0*52 „ 



It is probable that in general the firing buoy was not anything like 

 a metre out of line, and hence it is clear that it is useless to apply this 

 correction to the observed velocities. In any case a glance at the 

 Table will show that the irregularities observed are of such an order 

 as render any attempt to adjust the observations in this respect of 

 purely fictitious value. 



