201- MEMORANDA. 



from its construction, will be of very trifling cost). It con- 

 sists of an upper plate with raised edges, for the purpose of 



No. 1. 



holding the object-slide, and an under plate on which to 

 place the selenite, while to it are fixed two small pins, cor- 

 responding to two holes in the stage of the microscope, to 

 attach it, when in use, to the instrument; the same object 

 can, however, be effected by the ordinary clamping bar or 

 spring, where the microscope has them, in which case the 

 pins would not be required. In the second form, as shown 

 in drawing No. 2, the selenite holder is fixed on to a small 



No. 2. 



piece of tube, which turns round in another piece fastened to 

 the bottom plate, and in this way the rotation of the film is 

 effected. A very slight modification of this form will allow of 

 two or three selcnites being superposed where required. The 

 selenite stage being fixed to that of the microscope, as before 

 described, the necessary motions can be given by the proper 

 screws, when the instrument has a rackwork stage ; but where 

 this is not the case, the horizontal motion must be given to 

 the object itself, by sliding it along the top plate on which it 

 rests. — James Smith. 



The Collecting Bottle. — The accompanying drawings show the 

 design of a collecting bottle for aquatic larva?, infusoria, &c, 

 which may possibly be found convenient by mieroscopists 

 pursuing that line of study. It may be briefly described as 

 follows : 



Drawing No. 1 shows a wide-mouthed glass bottle, round 

 the neck of which a strip of gutta pcrcha is fixed, so as to 



