244 E. M. NELSON ON MAGNIFYING POWER OF A MICROSCOPE 



length. All other conditions being the same, the total mag- 

 nification will be proportional to the tube lengths used. 



Take the extraordinary difference of tube length shown by the 

 figures given below : 



Tube length. Magnification. 



14-6 in. 250 



5-3 in. 94 



Then 



Magnifica- 

 Magnification with long tube x short tube length 250 x 5-3 tion for 



short tube 

 length. 



Magnifica- 

 tion for 



Snort tube length. 5 # 3 ' long tube 



length. 



It is also worth mentioning that the diameter of the field may 

 be measured in millimetres, instead of inches, if millimetres are 

 used when determining the value of the eyepiece constant. And 

 members will probably find this a great convenience. 



J. Grundy.] 



Journ. Quekett Microscopical Club, Ser. 2, Vol. XII. , No. 73. November 1913. 



