450 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



No lengthy descrii^tion is needed, the principle being merely that 

 the lens necessary to correct the error of refraction of the eye commonly 

 used is fitted accurately into the centre of an aluminium carrier, so con- 

 structed as to form a cap which may be placed over the Microscope 

 ocular. In the case of a lens with cylindrical correction for astigmatic 

 error the vertical meridian is permanently marked on the carrier by 

 means of an arrow, as shown in the illustration. As most workers em- 



Fig. 80. 



ploy oculars of the same maker, the external diameter of which is 

 approximately the same, the cap may be made to fit them all by arrang- 

 ing to have the internal diameter adjusted to fit the largest ocular used. 

 The photograph has been taken from the cap made to the writer's 

 design by Messrs. Gary and Co., 7 Pall Mall. 



Simple Microscopic Place-finder.* — Fig. 80 illustrates a device, 

 described by T. Ries, by means of which much tedious searching of 

 microscopic fields may be avoided. The card may be attached to any 



* Zeitschr. wiss. Mikrosk., xxviii. (1912) pp. 289-91. 



