Velocity of Transmission of Disturbances through Sea-water. 529 



Thus the result of Class B may be expressed — 



Probable value of velocity at 14"5° C = 1775 + 27 metres per 

 second. 



The theoretical velocity of sound is 1508 metres per second. 



For Class C the mean temperature is 18 '3° C. Using V c to repre- 

 sent the velocity at 18'3°, and c being a quantity similar to the 

 quantity a in Class A, the system of resulting equations is — 



V c -0-3c = 197354 

 V c -0-3c = 199519 

 V c +0'2c = 192756 

 V c + 0-2c = 193659 

 V c + 0-2c = 187674 



Hence probable value of Y c == 194192, 



c= -14147. 



Mean as above = 194192 



If the method of least squares be applicable to such a small number 

 of values, then probable error of mean (Bessel) = 726 ; or by Pefcers's 

 formula probable error of mean = 807. Thus the result of Class C 

 may be written — 



Probable velocity at 18*3° C. = 1942 + 8 metres per second. 



The theoretical velocity of sound is 1525 metres per second. For 

 Class D, reducing the values to 19° C, the equations become — 



Substituting this value of c above, the values are — 



Departure from mean. 



193110 

 195275 

 195585 

 196488 

 190503 



-1082 

 + 1083 

 + 1393 

 + 2296 

 -3689 



r v d = 210000 



< V D = 192568 

 lV D + rt = 192327 



Hence probable value of Y D = 201284 



d = -8957 



The values of V D are therefore — 



2 n 2 



