the upper left for the shallow cast and upper 

 right for the deep cast. Use a convenient depth 

 increment for eacli cast which will allow suffi- 

 cient space for the maximum wire depth 

 sampled. 



Step 2. Across the top of the graph, lay off 

 the depth difference (L-Z) scale for each cast. 

 Use a convenient L-Z increment for each cast 

 which will allow sufficient space for the maxi- 

 mum Ij-Z observed. 



Step 3. From the origin (upi^er left or right 

 zero depth), construct a line making an angle 

 from the vertical which represents the wire 

 angle. This is done as follows : 



From a table of trigonometric functions, find 

 the cosine of wire angle (1). Subtract the 

 cosine from 1.000. Multiply the remainder by 

 100. Plot the product as L^Z at L equals 100, 

 and construct a line passing through the origin 

 and this point. 



Cosine of 13° is .974 

 1.000-.974 = .026 

 .026X100=2.6 



Step 4. Plot L-Z Ohs values at Wire Length 

 Depth (L) values; make a circle around each 

 point plotted. 



Step 5. Construct a reasonably smooth curve 

 through the origin of the graph and as many 

 points as possible. 



Step 6. From the curve, pick off L-Z values 

 for every Nansen bottle of the cast. Enter these 

 values in the appropriate L-Z Used block. 



Step 7. To detennine the accepted depth, sub- 

 tract L-Z Used value from Wire Length Depth 

 (L) value and enter the remainder in Accepted 

 Depth (D) column. 



F-7 Wire Angle (2) Measurements. — Wire 

 Angle (^) measurement is used by the oc«an- 

 ographer to assist him in verifying accepted 

 depth calculations obtained for a Nansen cast. 

 For example, if Wire Angle (1) and Wire 

 Angle (2) are nearly equal as in figure F-6, the 

 ship-wire system was probably relatively stable 

 during the descent of the messenger down the 

 wire. If the two wire angles, however, differ 

 significantly (5° or more), the probability 

 exists that either the ship was undergoing 

 accelerated drift, or the wire and bottles were 

 influenced by subsurface currents, or that both 

 conditions existed. 



Figure F-7 depicts examples of two deep cast 

 L-Z curves which do not follow the typical 

 classical pattern shown in figure F-6. Creclence 

 to the validity of the atypical L-Z curves is giv- 

 en by the observation of the second wire angle 

 measurement which in these examples differed 

 significantly from Wire Angle ( 1 ) . 



F-8 Subsurface Wire Angle Measure- 

 ments. — Subsurface wire angle measurements, 

 obtained with the subsurface wire angle indi- 



cator (WAI) described in paragraph E-6, 

 chapter E, are used to check accepted depth 

 differences between Nansen bottles on a cast. 

 For example, if the WAI reading between two 

 Nansen bottles is 6° and the bottles are Y 

 meters apart on the wire, the L-Z values for the 

 two bottles should differ by appi'oximately Y 

 Sin 0. The WAI is especially valuable between 

 the top two and the bottom two Nansen bottles 

 on deep casts. The other parameter, direction 

 wire is tending, that is obtained with the WAI, 

 is used as an indication of the true configuration 

 of the wire and may assist in the determination 

 of accepted depths. 



F-9 Checking A-Sheet Computations. — 



After the A-Sheet computations have been com- 

 pleted and the initials of the computer are 

 entered in the Computed By block, another per- 

 son should check the A-Sheet. To do this begin 

 with paragraph F-4, Correcting the Protected 

 Thermometer, and recompute the A-Sheet step 

 by step. Using a red pencil, indicate that an item 

 has been checked and is correct by placing a 

 small dot over the checked value. To make cor- 

 rections, line out the incorrect value and enter 

 new value. When the A-Sheet is completely 

 checked, enter initials in Checked By block. 



F-10 Correcting Reversing Thermometer 

 Temperatures with the Culbertson Slide 

 Rule. — The Culbertson slide rule is designed to 

 facilitate calculations of temperature correc- 

 tions and thermometric depths. In addition, the 

 rule has several other useful features, including 

 conversion scales, and a Temperature Depth 

 Salinity rule. The slide rule is circular, S% 

 inches in diameter, and has two movable arms 

 on one side and one on the other. Figure F-8 

 shows the side with two arms. This is the side of 

 the rule used for correcting reserving ther- 

 mometer temperatures. To calculate protected 

 and unprotected thermometer corrections (Cp 

 and Cu) with a Culbertson slide rule, proceed as 

 follows : 



Step 1. Using the values for thermometer 

 number 327-64 in Figure F-9, set (see footnote) 

 the arms on T' and t on the linear temperature 

 scale surrounding the striped graph. Set the 

 long arm on the larger value and the short arm 

 on the smaller value, e.g., T' (15.18°) and t 

 (18.4°) (fig. F-10). 



Step 2. Move the arms until the short arm is at 

 0°(fig.F-ll). 



Step 3. Under 109.38° (Vo + T') (94.2-h 

 15.18) on the long arm, read .06° (Cp) on spiral 

 stripes. If T' is less than t, the correction (Cp) 

 will be negative; if T' is greater than t, Cp will 

 be positive. 



Step 4. Enter Cp (-.06°) in Cp/6'u column 

 of the A-Sheet and calculate Tw (15.14°). 



F-9 



