METHODS EMPLOYED IN CALIBRATION OF MERODIIIAL THERMOMETERS. 193 



Table XXXVIII. Hence the corrected value of Thread I. is obtained aa 

 in Table XXXVIII. 



Table XXXVIII. 

 Corrected Mean Lengths of Threads. 



Subtracting this mean thread-length from the uncorrected lengths 

 given in Table XIX., the errors of the additional measures of Thread I. 

 are found, and entered in Column I., Table XXXIX. 



The corrections of the initial point.'^ between 116 and 122 beino- 

 known from the first mean curve, which is complete up to 123, they are 

 entered in Table XL., and by subtracting from these the errors of the 



Table XXXIX. 



Errors of Additional Mcasitres = Jj — Z, in terms of 0°-001. 



additional measures in Table XXXIX., the corrections for the upper 

 points of the first three additional measures of Thread I. are found and 

 entered in Column I., Table XL. The points to which these correspond 

 are given in Column I., Table XXI., and by their aid the correction curve 

 given by Thread I. can be prolonged as in fig. 2, Plate III. 



Using this prolongation, the mean curve can now be prolonged for 

 two or three degrees by means of all the ten curves — viz., nine in fio-. 1, 

 Plate II., and one in fig. 2, Plate III. — i.e., it is prolonged far enough 

 to take out, as in Column II., Table XXXVIL, all the corrections for the 

 upper points of Thread II. The same process can then be repeated with 

 this thread, and thus gradually all the ten curves, by means of which the 

 first mean curve is constructed, are formed — the initial point of each 

 additional measure being determined, with the full accuracy of which 

 the first approximation is capable. 



(33) The second approximation is then carried out in exactly the 

 same way. 



1882. 



