472 NOTES AND MEMORANDA. 



the fine adjustment was divided for the measurement of the thickuess 

 of sections, but in future it is proposed to effect this object in a 

 different manner by divisions engi'aved ujion the limb and the sliding 

 portion of the coarse adjustment (a vernier). The right trunnion 

 carries a clamp to fix the instrument at any angle. The head of the 

 tube or body carries a bevelled disk which is divided to 10^ spaces. 

 A corresponding disk with an index is attached to the bottom of the 

 analyzer-fitting, and rests directly upon the fixed divided disk ; so that 

 the analyzer can be set in any required position, and any amount of 

 revolution imparted to it can also be registered. The eye-piece, when 

 inserted, is kept in a fixed jjosition by a stud, which falls into a small 

 Blot. Crossed cobwebs are fixed within the eye-piece for the purpose 

 of centering the instrument. A small plate of calc-spar, cut at right 

 angles to the optical axis, is mounted in a little metal ring, which can 

 be placed between the eye-glass and the analyzer for stauroscopio 

 examinations. 



At the lower end of the Microscope-tube a slot is cut to receive a 

 Klein's quartz plate or a quarter-undulation plate, both of which are 

 set in small brass mounts. When these are not in use the aperture 

 can be closed by means of a revolving collar. 



The stage is circular, and capable of concentric rotation, and it is 

 divided on the margin to 360'^. A vernier is attached to the front of 

 the stage, giving readings to one minute. The edge of the stage is 

 milled, and rotation is imparted by hand. 



The polarizer slides into a fitting which is fixed to an arm jii voted 

 on the lower, movable surface of the stage, so that it can readily be 

 displaced when ordinary ti*ansmitted illumination is required, and 

 replaced with equal facility. 



Two little lenses, affording a strongly-convergent pencil of light, 

 are set in metal rings which drop into the top of the fitting which 

 surrounds the polarizing prism. When these are employed and the 

 analyzer is used, without lenses in the eye-piece (a separate fitting is 

 supplied for this purpose), examinations of the rings and brushes 

 presented by sections of certain crystals, can be advantageously carried 

 on, and a quarter-undulation plate can also be employed when needful. 

 The lower end of the fitting which carries the polarizer is surrounded 

 by a divided disk, turning beneath a fixed index, so that any jiosition 

 of the prism can be recorded, and the rotation imparted to it can be 

 measured. 



From the foregoing description it Nvill be seen that this instrument 

 is capable of performing the fimctions of an ordinary Microscope, 

 a polariscope, a stauroscope, and, to some extent, a goniometer. A 

 spectroscope could be fitted to it if needful, as well as an apparatus 

 for heating sections of crystals. 



Female Microscopical Society. — We gather from a report of a 

 *' regular meeting " of the Microscopical Society of Wellesley 

 College, U.S., on March 15, reported in the 'American Journal of 

 Microscopy,'* that it consists exclusively of lady members. The 



* ' Am. Journ. Micr.,' iv. (1879) 71. 



