126 



THE AMERICAN MONTHLY 



[July, 



jects, taking either from the objects 

 themselves by aid of the microscope, 

 o'' else from good wood-cuts — which 

 is often the better plan — than to 

 grapple with the difficulties in using 

 the projecting microscope. We re- 

 gard the latter as a useful instrument 

 for popular demonstrations, and, no 

 doubt, it has a limited sphere of useful- 

 ness in more strictly scientific work, 

 but until it is greatly improved in sev- 

 eral respects, it cannot be of very 

 great value to lecturers upon scientific 

 subjects, 



A Large Microscope. 



FrG. 23. — Dr. Deecke's Microscope. 



Many of our readers have heard o^ 

 the large microscope used by Dr. T. 

 Deecke, of the New York State Luna- 

 tic Asylum for the examination of 

 large sections of the entire human 

 brain, and for other purposes. These 

 celebrated sections sometimes meas- 

 ure nearly six inches in diameter, and 

 not more than -ilo-slo of an inch in 

 thickness. We take pleasure in giv- 

 ing an illustration (fig. 23), of Dr. 

 Deecke's microscope, taken from the 

 Journal of the Royal Microscopical 

 Society. 



It was made in 1876. The mechani- 

 cal stage is 12 inches square, hav- 



ing 8 inches motion. The ingenuous 

 method of inclining the instrument, 

 by means of a screw at the base, will 

 be readily understood from the figure. 

 TJie arm carrying the tube is 13 .J 

 inches in length. A slide 10x8 in- 

 ches can be laid on the stage. 



Eveuiugs with the Microscope. 



II. MULTIPLE IMAGES. CRYSTALS. 



In a preceding article were given 

 instructions for mounting the eyes of 

 insects in balsam. Perhaps on the 

 whole it is better to mount them dry. 

 The process for. cleaning them is the 

 same as that previously described, the 

 only difference in the whole operation 

 being in the mounting on the slide, 

 which will now be described. 



First we would allude to the prepa- 

 ration of insects' eyes for showing 

 multiple images, that is, so that each 

 facet of the compound eye will act as 

 a lens, forming an image of an object 

 placed behind it at its conjugate fo- 

 cus, so that in the microscope may be 

 seen an image in each of the liny 

 lenses. 



To do this it is only necessary to 

 clean the eye thoroughly, which had 

 best be done with water and a brush, 

 and then mount it dry. 



The convex form and chitinous na- 

 ture of the eye makes it rather troub- 

 lesome to mount. It should be spread 

 out flat on the slide, but in order to 

 get it flat it must be cut around the 

 edges, otherwise it will be sure to 

 break, and irregular cracks will ex- 

 tend across it. So make a few slits 

 inward around the circumference, dry 

 the specimen thoroughly, and then 

 place it in the centre of a clean slide 

 having a thin ring of plain shellac al- 

 ready hardened upon it. upon which 

 the cover-glass may rest. The object 

 of this ring, is to prevent any cement 

 that may be applied, from running 

 under the cover. Now apply a fresh 

 coat of shellac to the ring, and im- 

 mediately put on the cover-glass. 

 Then flatten the eye out by applying a 



