58 



OBSERVATIONS AND RESULTS IN PHYSICAL OCEANOGRAPHY 



Table 3. Showing difference in time required for first and succeeding echoes 



9.6 



9.6 4.65 



8.7 



8.6 4.25 



9.7 4.7 

 10.2 5.0 

 10.1 



10.2 4.85 

 9.8 



9.9 4.80 



9.8 



9.7 4.75 



10.3 5.0 

 3.5 



3.5 1.65 



11.0 5.5 



11.1 5.5 

 11.4 



11.6 5.80 



11.5 



11.2 5.65 

 10.1 



10.1 5.05 



11.7 



11.8^ 5.70 

 3.9'> 0.70 



4.95 



4.40 



5.0 



5.2 



5.30 

 5.05 



5.00 

 5.3 



1.85 



5.5 



5.6 



5.70 

 5.70 

 5.05 



6.05 

 0.80 



+ 0.30 



'+0.15 

 + 0.3 

 + 0.2 



+ 0.45 

 Vo.25 



+ 0.25 

 + 0.3 



+ 0.26 

 + 0.00 

 + 0.1 



-0.1 6 



+ 0.05 



+0.66 



+ 0.35 

 + 0.10 



Mean and probable error= +0.113 ±0.028 



a Time questioned in original record. 



*^Time for first four echoes. 



"Time of second echo apparently in error by one second. 

 •^Time for first five echoes. 



soundings, the ratios of true depth to indicated sonic 

 depth have been of the same order of magnitude and 

 less than unity. This can probably be reconciled with 

 the comparison of stop watch and chronometer by con- 

 sidering that the stop watch had a faster rate during the 

 first part of a run than during the latter part, such as 

 the second hour, and that the initial fast rate was main- 

 tained during the first fifteen minutes. This seems to be 

 be a reasonable assumption, and on such a basis the dif- 

 ferences between the timing factors found for the shot- 

 gun soundings and the first and second periods of the 

 sonic depth finder are attributed to the changing rate of 

 the stop watch. Viewed in this light it is to be noted that 



when these three timing factors are plotted against time 

 they fall practically on a straight line. Such a plot is 

 shown in figure 2, in which the date of the first adjust- 

 ment of the depth finder is taken as May 28, 1928; the 

 date of the shotgun ratio is taken as the mean date of the 

 comparisons on which it is based, December 19, 1928; 

 and the date of the second adjustment of the depth finder 

 is taken as February 19, 1929. 



These timing factors place the shotgun soundings 

 and the sonic depth finder soundings all on a common 

 basis, which is referred to the unprotected deep-sea re- 

 versing thermometers for a standard of depth. 



