68 CLIMATIC CYCLES AND TREE-GROWTH 



Analysis — Three analyses were made, namely: (1) the full length 

 of the group curve, using maxima; (2) the part of the group curve 

 subsequent to 1750 a. d., using maxima; (3) the part of the group 

 curve subsequent to 1750 a. d., using minima, that is, plotting an 

 inverted curve and then cutting out and analyzing the higher (nega- 

 tive) ordinates as usual. 



Precautions — Knowing the possibility of prejudice and systematic 

 error in analyzing this large number of curves, several precautions 

 were observed: (1) Settings of the White cyclograph were made with- 

 out knowing what the reading was going to be; (2) full analysis of 

 each curve was made without knowing which curve it was; (3) each 

 of the three analyses was carried through the complete list of curves 

 in one continuous sitting of four or five hours, so that possible errors 

 of adjustment or of judgment would apply equally to all groups; (4) 

 the instrument was calibrated from time to time with standard curves, 

 and its errors were of the order of one-tenth of a unit of period, which 

 is less than the error of an average setting, which is one to three 

 tenths of a unit, depending on conditions. Four critical parts of the 

 reduction process were invariably done by the writer, namely, dating 

 the rings, drawing the standardizing line, marking the cutting line 

 for the cycle plot, and making the cycle analysis. Other parts were 

 done mostly by assistants, such as mounting, measuring (checked 

 afterwards by the writer in most cases), tabulation, plotting, smooth- 

 ing, and tracing and cutting the cycle plot. 



Analysis report — A cycle is reported below only when it occurs in 

 two of the three analyses, and its relative excellence is shown by a 

 number in parentheses following the cycle-length. This number may 

 be considered a "weight" and so an approximate amplitude. Unit 

 weight, meaning medium or average conspicuousness of the cycle, is 

 omitted. Weight 2 means a fine cycle and weight 3 a remarkable 

 cycle as viewed in the cyclograph. Cycles occasionally show a lesser 

 secondary maximum and very rarely two secondary maxima. In 

 such cases the fraction \ or \ respectively, in the parentheses with 

 the weight, gives indication of this doubling or tripling. 



Abbreviations — For convenience, the names of the groups are 

 sometimes reduced to an abbreviated form which consists of some 

 initial letters as suggestive as possible. These letters are given after 

 the group title. 



ARIZONA REGION 



FIRST FLAGSTAFF GROUP (FL) 



This group was collected in 1906, 1 or 2 miles west of Woody 

 Mountain and some 10 miles southwest of Flagstaff. Nineteen trees 

 numbered 7 to 25, were used; Nos. 1 to 6 were not preserved and there- 



