reducing deep sea refraction data. The several graphs 
that have been found helpful in carrying out the 
reductions have also been included in such a manner that 
they may be used directly from the reporte 
II. Shot Instant Correction 
In a two ship refraction operation one ship, say 
the Atlantis, heaves to and lowers her hydrophones prepara- 
tory to receiving. The Caryn then proceeds on course shooting 
the necessary shots to make the profile. After completing the 
shooting, the Caryn heaves to and prepares to receive, as the 
Atlantis gets underway on course toward the Caryn, firing 
shots to complete the reverse profile. 
The shot instant is picked up on the shooting ship 
and sent over the air to the re cei ineten ike where it is 
recorded on the refraction records Simultaneously, a shot 
record is made on the shooting ship. Several identifiable 
buzzes and signals are sent over the air after the shot and 
recorded on both the shot and refraction record in order to 
allow correlation of the two records and location of the 
shot instant on the refraction record when, due to poor 
radio contact or other causes, the shot instant is not 
recorded on the refraction record. FEesides allowing this 
correlation the shot record is useful in determining the 
depth of the shote 
After locating the shot instant on the refraction 
record either by direct reading or by correlation with the 
