DEPTH TO BOTTOM AT CARNEGIE STATIONS 



At a number of stations from station 7 to station 49 

 wire depths were obtained by the 4 -mm wire. In all 

 cases a water bottle provided with an unprotected and a 

 protected thermometer was attached to the end of the 

 wire and the depth was computed from the indications of 

 the thermometers. The accuracy of this method has 

 been discussed previously. No independent determina- 

 tions of depth by means of the 4-mm wire were made and 

 it is, therefore, unnecessary to enter on a discussion of 

 the relation between wire length, wire angle, and depth 

 at these stations. 



At the greater number of the stations from 40 to 162 

 the depth was determined by means of sounding with 

 piano wire. The wire angle was in many instances very 

 great and it is, therefore, necessary to examine the re- 

 lation between wire length, wire angle, and depth in 

 these cases. In a number of cases a reversing frame, 

 carrying two thermometers, one unprotected and one 

 protected, was attached to the end of the wire. This 

 frame was released by a propeller and according to ex- 

 periments it had to be hauled up a distance of 25 meters 

 before it \as reversed. From the indications of the two 

 thermometers the depth at which the frame was re- 



versed can be computed with an accuracy of about +0.5 

 per cent. Adding to this depth the distance of the frame 

 from the lead at the end of the wire and the distance of 

 25 meters which the frame had to be hauled up before 

 reversal, the depth at the station is obtained with the 

 same accuracy. Omitting the observations at eight sta- 

 tions at which the frame evidently had reversed at a 

 wrong level, thirty-four stations remain from which cor- 

 responding values of depth, wire length and wire angle 

 are available. The data from these stations have been 

 compiled in table 1 in which the cosine of the wire angle 

 and the ratio between the observed depth and the wire 

 length also are entered, the latter under the headline 

 "depth factor." It is seen that the depth factor is usual- 

 ly smaller than the cosine of the wire angle at the sur- 

 face, which means that the wire angle decreased when 

 approaching the bottom. 



In figure 1 the depth factor has been plotted against 

 the wire angle and the single values are grouped around 

 a smooth curve. The scattering of the values is small, 

 considering that the depth factor for any given wire angle 

 depends on the curvature of the wire which again is con- 

 trolled by the change of current with depth, and by the 



Table 1. Comparison between wire length, wire angle, and thermometer depth at stations where 



sounding with piano wire was undertaken 



Sta- 

 tion 

 no. 



Wire 

 length, 

 meters 



Wire 



angle, 



degrees 



Cosine 



of 



wire 



angle 



Ther- 

 mom- 

 eter 

 depth, 

 meters 



Depth 

 factor 



Adopt- 

 ed 

 depth 

 factor 



Wire 

 depth, 

 meters 



Thermometer 



depth minus 



wire depth, 



meters 



47 



