550 



Transactions of the Society. 



r = ± 0-4 div. = + 0-02 ^ 

 r = ± 0-1 div. = ± 0-007 /x 



Average deviation from mean = 0-5 div. = • 2 /x. 

 Greatest deviation from mean =1-0 div. = • 05 /x. 



The same instruments, except 2 mm. Himmler homogeneous 

 immersion objective, one division = 0*02154 fx. Book W, p. 80. 



r = ± • 9 div. = + • 02 fi 

 r = ±0-3 div. = ± 0-006 ^ 



Average deviation from mean = 1 • 1 div. = 0*02 /x. 

 Greatest deviation from mean = 2-1 div. = • 05 /x. 



The same instruments, except Zeiss ^-in. objective, one division 

 0-015/x. BookW, p. 80. 



