THE TRUSTWORTHINESS OF THERMOMETERS USED 

 BY CALIFORNIA FRUIT GROWERS 



By Dr. Ford A. Carpenter, Consulting Meteorologist 



(Illustrated by the Author) 



"Are your temperature readings accurate?" is one of the ques- 

 tions being asked with increasing frequency in California. It may 

 be answered in the affirmative, if (1) the thermometer has been 

 properly made or tested, (2) if it has been properly located, (3) 

 if it has been correctly read, and (4) if the readings have been 

 promptly recorded. 



It is the purpose of this pajDer to present some of the difficulties 

 encountered in the manufacture of thermometers ; to describe some 

 of the methods used in their calibration; to show how they may be 

 placed in localities giving the best results ; to explain how personal 

 errors may be avoided ; suggest the making of satisfactory records ; 

 to enumerate the results of a year's tests of various t3'pes of 

 thermometers and summarize the relative accuracy of the different 

 types in use by orchardists and others. 



THE NECESSITY OF A THERMOMETER TESTING BUREAU 



It is an unsolved problem whether credulity or incredulity 

 is responsible for the greater amount of error. In the matter of 

 thermometers ordinarily in use there appears to be no doubt at all 

 about the solution: it may be said without hesitation that it is the 

 former, for not one person in a hundred but what believes that 

 the thermometer is reliable. This; is not only true of the processes 

 of taking temperature readings in the citrus orchards of California 

 or elsewhere, but the same criticism holds good in the use of 

 clinical thermometers and thermometers when applied in the arts 

 and in the industries. Human nature is apt to accept a printed 

 statement, or an engraved or stamped scale as being correct without 

 personal investigation. And is it not natural.'' We never think of 

 checking up the accuracy of a foot-rule or a yardstick; it is accepted 

 as being dependable. If the making of thermometers was simply 

 a matter as dividing off the tenths or sixteenths of an inch on a 

 wooden or metal strip, most of the difficulties in the use of a 

 thermometer would be solved. 



When the practical research department, dealing with meteor- 

 ology applied to agriculture and aeronautics, was created in the 

 Los Angeles Chamber of Commerce as described in a Bulletin of 

 this Society*, one of the objects set forth was the standardization 

 of certain instruments used in industry. A few tests were con- 

 vincing proof that one of the most important fields for investiga- 

 tion was the examination and certification of thermometers used 

 by the citrus growers of Southern California, so, in November, 

 1920, a testing bureau was established. 



*Bull. So. Cal. Acad. Sci., Vol. 19, Pp. 9-11. 



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