J. F. Martley 249 



tangentially, the periods are not rigidly fixed with reference to the 

 growth-rings, or in other words the periods are only approximately 

 simultaneous, and finally the inclination of the grain at corresponding 

 phases of a period vary from stick to stick. The result is that, though the 

 inclination of the grain alternates between left-handed and right-handed 

 when traced ring by ring from the centre to the exterior, around no 

 ring is the inclination of the grain uniform while often it may change 

 several times from left-handed to right-handed on being followed round. 

 All these points can be followed in a careful scrutiny of the transverse 

 series of curves. 



The course of the grain having been determined there still remain 

 some points of secondary importance to be investigated, namely the 

 relations that exist between period length, amplitude, width of rings and 

 age to tree. 



In determining average period lengths and average amplitudes all 

 doubtful cases were neglected in transitional regions where one set of 

 periods w T as vanishing and another set appearing in its place. 



The radial distance between two successive maximum right-handed 

 or left-handed inclinations was used for obtaining average period lengths 

 rather than the distance between succeeding vertical phases, since the 

 former was likely to give more reliable figures as it may happen that a 

 period may remain completely right-handed or left-handed in its in- 

 clination ; for example, the period between the 47th and the last ring in 

 the 16th stick of the longitudinal series which is wholly left-handed. 



In Tables III and IV are given the period lengths in centimetres for 

 the sticks of the longitudinal and transverse series respectively, and in 

 addition is given the average period length for each stick and also 

 the average length of the successive periods throughout the series. 



The figures in Table III show that the greatest period length (4-15 

 cms.) in the longitudinal series is reached by the period comprised between 

 the 15th and 23rd rings and that subsequently a decrease in the period 

 length sets in. Correlated with the gradual shift of the last two periods 

 towards the exterior (see Fig. 4) the average period length at the different 

 levels in the longitudinal series shows a gradual increase from stick 6 to 

 stick 18 (last column, Table III). 



The measurements of tbe period lengths of the transverse series 

 (Table IV) demonstrates that the average period length increases with 

 age, as in the longitudinal series, to a maximum (4-35 cms.), after which 

 it decreases. On comparing together the average period lengths of the 

 different sticks it is seen that the period length varies directly with the 



