Page 587 radio acoustic ranging 6342 



surface observations, a number of these may be recorded on one copy, the date of 

 each observation being entered in the left-hand column. The time of a single observa- 

 tion should be recorded in the proper column, but only the times of beginning and 

 completing a serial temperature need be recorded. The depth of an observation should 

 be indicated to the nearest half fathom for the first 100 fathoms below the surface and 

 to the nearest fathom for greater depths. Care must be taken to record the actual 

 depth of observation. The bottom observation should be indicated by a Z? after the 

 recorded depth. Where the position of an observation is known accurately, the latitude 

 and longitude should be given to the nearest tenth of a minute, but for a serial tempera- 

 ture, where the ship has drifted considerably, the probable mean position to the nearest 

 half minute is all that is warranted. 



The observed temperatures should be read and recorded to the nearest tenth of a 

 degree centigrade and the corrected values entered in the column provided for that 

 purpose (see 4713). 



Four columns are provided for the data to determine the salinity by hydrometer. 

 Under the two columns headed "Specific gravity," spaces are provided for recording 

 the observed density, or apparent specific gravity, and the corrected observation. To 

 the right of these is another two-column space headed "At temp." in which the observed 

 and corrected temperature of the water sample should be entered. (See 6331.) The 

 maker's numbers of the reversing thermometer and the hydrometer — ^not the National 

 Bureau of Standards numbers — should be recorded in the spaces provided. 



In the "Remarks" column the character of the bottom should be recorded on the 

 same line with the observations at the bottom depth. In this column the state of the 

 weather and the condition of the sea should also be entered. 



The salinities determined from the specific gravity measurements, and the velocities 

 computed from the temperature, salinity, and depth determinations, are also recorded 

 on Form 717. The determination of salinities from the observations is described in 

 6331 and the computation of velocities is described in 6343. Salinities determined by 

 titration, or by any other method, are also recorded on this form. 



Rubber Stamp No. 40 should be used in the lower right-hand corner of the form 

 and the initials of the persons who observed and recorded the data, computed the 

 salinities and velocities, and checked the computations, should be entered in the spaces 

 provided. 



6342. Temperature and Salinity Graphs 



Simultaneously with the serial temperature observations, the corrected tempera- 

 tures and the salinities should be plotted as graphs on Form B-1528-5, designed for 

 this purpose. This should always be done to ensure that the number of observations 

 is sufficient and that they are correct. The temperature and salinity graphs aid in 

 detecting any erroneous observations and in determining at what depths additional 

 observations are required. If there is any uncertainty in drawing any part of the 

 temperature curve, additional observations should be taken. 



In most localities the temperatures in the upper layers of water generally cover a 

 wider range and are more variable. Therefore, in plotting the temperatures on Form 

 B-1528-5, the curve should be plotted in two sections; a shoal section from the surface 

 to 100 or 120 fathoms, and a deep section from 100 to 1,200 fathoms. The whole of the 

 depth range of the ordinate scale should be used for both curves, the shoal section being 

 on a scale 10 times as large as the deep section. The temperature at 100 or 120 fathoms 



