in some container or bucket. No attempt ever has been made to stand- 

 ardize the thermometer, bucket, or techniques. Therefore, although 

 many observations are of high quality, many are poor. The observation 

 is a point type that is recorded by hand. Bucket thermometers gener- 

 ally are graduated in 1°F divisions. Improved bucket thermometers have 

 an elongated scale which permits easier reading to ±0.1°F. If properly 

 taken, bucket temperatures can be obtained to this accuracy. 



2. Intake thermometer 



Another large percentage of surface water temperatures is 

 obtained from the intake thermometers on ships. Very often these 

 temperatures may be slightly higher than the in situ temperature. This 

 temperature difference is caused by the location of the thermometer 

 inboard of the intake opening and the heating effect of the ship itself. 

 On some ships, temperatures are automatically recorded, but on many 

 they must be read and recorded by hand. Surface temperatures with 

 more accuracy and in greater quantity can be obtained with a properly 

 designed, properly located instrument. 



3. Bathythermograph (BT) 



The existing continuous subsurface temperature measurements 

 for the upper 900 feet of the oceans have been obtained with the bathy- 

 thermograph (BT). This instrument obtains a continuous trace of temp- 

 erature versus depth. Three models exist for use to depths of 180, 

 450, and 900 feet, respectively. Accuracies of ± 0.2°F and ± 1 percent 

 of full scale can be obtained from a BT that is carefully calibrated 

 and expertly handled. However, study of the BT data received in the 

 Hydrographic Office indicates that this accuracy rarely is achieved. 

 The main reasons for inaccuracy are mishandling and abuse of the 

 instrument and the long intervals between calibrations, which must be 

 made at shore stations because of the rather elaborate equipment 

 needed to produce the pressures associated with depth. A BT in use 

 is checked by comparing its surface temperature indication against 

 that of a bucket thermometer. However, differences between the two 

 values may not necessarily mean that the BT is at fault. 



The BT record also does not lend itself readily to mass data han- 

 dling methods. The present method of recording BT temperature 

 values on punch cards from discrete points on the trace negates to a 

 large extent the advantage of the continuous trace. The fact that as many 

 as three punch cards are required to record the desired data from a 

 single BT trace gives an idea of the magnitude of the problem. 



Ill -4 



