BAIRD &.TATLOCK (LONDON) LTD. 



SPECIFICATION, see page 266. 



E. F. equivalent focal length. 

 1344 1 Huyghenian Eyepieces for Bausch & Lomb's Microscopes. 



The eyepieces in this series are marked according to their magnification when used as magnifiers. -This is 

 equal to the distance of distinct vision for a normal eye (250 mm. or 10 in.), divided by the focus of the eyepiece. 



The lower focal point in this series of eyepieces is situated somewhat higher than usual, thereby increasing the 

 optical tube length the distance between the upper focus of the objective and the lower focus of the eyepiece. 

 The magnifications obtainable with these eyepieces are therefore greater than those obtained with the usual 

 eyepieces of the same equivalent focal length, as may be seen in the magnification table below. The whole series 

 of eyepieces is par-focal, that is the lower focal planes of all lie at the same distance below the eye-lens, so that in 

 interchanging them only a very slight change of the fine adjustment is necessary. 



The eyepieces, unless otherwise ordered, measure 23 mm. outside diameter, and conform to the European 

 standard size. If desired, the older size (25 mm.) will be furnished, the diameter of the draw tube being increased 

 accordingly. 



When one eyepiece only is purchased with an outfit, we recommend the 6.4X or the 7.5 x , believing these 

 magnifications to be most serviceable for general work. In case two eyepieces are to be used, we recommend the 

 5X and iox, or the 6.4 X and tox . Higher powers can be furnished if desired 



1344 



E. F.=equivalent focal length. 



Table of Magnifications and Real Fields. Tube length = 160 mm. 

 = 250 mm. (Objectives No. 1343 and eyepieces No. 1344). 



Projection distance 



Objectives. 



; 



Eyepieces. 



(CHEMICAL AND SCIENTIFIC APPARATUS AND PURE CHEMICALS. 



