Pocket -thermometer temperatures are single 

 readings taken daily when the lamprey-control de - 

 vices were serviced. The time of day at which these 

 temperatures were taken varied randomly according 

 to the schedules of the weir attendants. 



Thermal data in this report are presented in in- 

 dividual tables for each stream in the form of aver - 

 age temperature for each 10- or 11 -day period. The 

 volume of the data available made the presentation 

 of daily readings impractical; furthermcare, the tem- 

 perature trends as indicated by averages are probably 

 more useful than daily readings. 



than the nearest °F. The instruments used were very 

 accurate within their limitations and did not vary in 

 precision. The principal disadvantage of a single 

 reading in computing averages is that it usually does 

 not represent the true mean for the day. Apparently, 

 these variations tend to equalize when used in com- 

 putation of averages. 



Data transcribed from field forms and thermo- 

 graph charts have been recorded only to the nearest 

 Fahrenheit degree. This level of accuracy has been 

 selected as consistent with methods of collecting. 



MAXIMUM -MINIMUM READINGS AND SINGLE 

 READINGS WITH A POCKET THERMOMETER 



The relative dependability of daily maximum - 

 minimum temperatures as compared to single daily 

 pocket -thermometer readings had been argued for 

 some time. The data collected during lampiey- 

 control operations supplied an opportunity to compare 

 closely these two methods of recording temperatures. 

 The daily pocket -thermometer temperatures and the 

 daily mean of maximum -minimum reading? as read 

 from thermograph charts agreed closely. Data on 

 temperatures taken by both methods on several streams 

 yielded 10- or 11 -day averages that never differed 

 more than 4* F. and usually disagreed by less than 

 2° F. (See tables 1, 2, and 3 for examples of the 

 records. ) Daily readings differed by a maximum of 

 11° but were usually less than 5°. 



These disagreements become even less conse- 

 quential when the limitations of the two methods are 

 considered. Thermograph charts were calibrated in 

 2* graduations, and the width of the pen line was usu- 

 ally 1° or mOTe. The accuracy of interpretation was 

 probably no closer than 1 or 2*. FurthermOTe the {we- 

 cislon of these instruments displayed a tendency to 

 vary under field operating conditions. Althou^ the 

 instruments were adjusted frequently, their readings 

 undoubtedly were in errof by several degrees at times. 



Pocket thermometers, also, were calibrated in 

 2* graduations and hence could not be read closer 



