MEMORANDA. 203 



light covers, and may either be fastened by an ordinary 

 brass clasp, or by a lock, as in the drawing ; at either end is 

 a small leather or cloth flap to keep out the dust. The one 

 figured as above will contain twelve dozen objects; but by 

 putting eight slides in a row, and doubling the number of 

 leaves, a single cabinet would hold 384< specimens: but both the 

 size of it, and the number of objects it may be made to con- 

 tain, is more a matter of individual convenience than other- 

 wise ; and where the quantity of any particular class of objects 

 is sufficient, separate cabinets might be had for each, as for 

 instance, Diatomaceae and Desmidiaceae insect prepara- 

 tions, &c, &c. Besides the ease of reference, which may be 

 further facilitated by an index (each space being numbered), 

 and by having particular classes of objects in separate books, 

 as above proposed, the cabinet can be carried about from 

 place to place, without in any way disturbing or moving the 

 specimens ; and this is sometimes an advantage, although but 

 a trifling one. 



I have lately been given to understand that this form 

 of cabinet is not altogether new, and that I cannot lay claim 

 to having been the first to propose it ; yet I have ventured to 

 put forward the above drawings and description, from the 

 circumstance of my own having met with so much approval 

 from every one who has seen it, and as I am not aAvare that 

 the plan has as yet been adopted or brought specially forward 

 in any way. — James Smith, 21, Soley Terrace, Pentonville. 



A new Polarising Stage. — The accompanying drawings show 

 two different constructions of a selenite or polarising stage, 

 which I have designed to obviate a slight difficulty in the 

 examination of objects by polarised light, viz., that of 

 having to alter the focal adjustment of the microscope every 

 time the selenite is placed under the object to be examined, 

 or removed from it ; but by the use of either of the above 

 forms of stage, the particular object to be examined having 

 been once found and properly focused, it can be viewed, in 

 the first place, by the polarising prisms alone, and after- 

 wards with the selenite interposed, which can be exchanged 

 for one or more of different tints, without in any way moving 

 or disturbing the slide ; and thus I conceive that, in instru- 

 ments that are not otherwise specially adapted for the pur- 

 pose, the various phenomena of polarised light (as applied 

 to the microscope) may be more easily and satisfactorily 

 observed. 



Drawing No. 1 shows the simpler form of the stage (which, 



