546 



Transactions of the Society. 



Using the Spencer 4 mm. objective, with which one division 

 = 0*047 fi on the first T £ mm. we have : — 



r 

 r 



= ±1-13 div. = ± 

 = +0-25 div. = - 



05 p 

 01 fi 



As before stated, Mr. Keeley's method requires two readings 

 on each side of each defining line to make a complete observation. 

 Below are given ten complete observations on the first -fa mm., 

 using the -fo Tolles objective, with which one division = ■ 263/a : — 



= + 



r = 



— J. 



14 div. = 

 04 div. = 



- 



04 fi 

 01 fi 



