456 



Table IV. shows the mean difference of the minimum from the arithmetic mean of adjacent ordinary 

 leadings, for each 2-hour interval, during each individual month from February, 1902, to October, 1903. 

 Subsequent to the latter date the number of observation hours was reduced, and so the results ceased to 

 be comparable. Table IV. shows also the mean of the twelve 2-hourly differences for each month. 



TABLE IV. Excess of Mean of Ordinary Readings at Beginning and End of 2-hour Interval over 



Corresponding Minimum Heading. 



TABLE V. Excess of Mean of Ordinary Readings at Beginning and End of 2-hour Interval over 



Corresponding Minimum Reading. 



Table V. contains similar data to Table IV., but gives the mean of the results from corresponding 

 months of the two years. In Table V. we have the mean difference for the month, exhibiting a fairly 



