M. J. Tucker and A. R. Stubbs 309 
UPPER SIDE LOBES 
SEA SURFACE 
SEA BED 
Fig. 16.9. Diagram showing vertical arrangement of beams of the asdic mounted in the R.R.S. "Discovery II.” 
studies, but also with the geological application in mind, and has in practice 
become a most powerful geological tool. (See Tucker and Stubbs [9] for a detailed 
description of the instrument and Stride [10] fora survey of the geological uses.) 
The asdic points sideways from the ship, with a narrow beam of 1.3° in plan 
view and a wider beam in the vertical plane (approximately 11° in the usual ar- 
rangement). The main particulars are: 
ITESCWOMEY cao donc coboa0 do BO NCOs 
Pulse length..............0.3 to 3 msec (normally used at 1 msec) 
PUSS OWEIE 5 oo oo oo 000008 0 OW) Wy 
Repetition rate... -..... . 1 pulse perm sec 
Maximum recorder range... . . 800 PORE EMG 
| 
>) 
Wl 
=I 
= 
N 
x 
Oo 
a 
a 
a 
< 
the 
Fig. 16.10. Asdic record showing strata on the sea floor in 
Bristol Channel. 
