1884.] 



MICROSCOPICAL JOURNAL. 



23 



mended to use as large a condensing 

 lens as possible, or perhaps a large 

 glass ball filled with water, in order 

 to secure an evenly illuminated field 

 of view without moving the flame too 

 near the microscope. The condens- 

 ing lens or the glass ball is placed in 

 such a position between the lamp 

 and the microscope that an image of 

 the flame is projected on the plane 

 mirror. 



When, in using immersion lenses, 

 very oblique illumination is desired, 

 or when dark field illumination under 

 high amplification is used, it is advan- 

 tageous to place a drop of water on 

 the upper surface of the condensing 

 lens of the apparatus, so as to fill up 

 the space between it and the under 

 side of the object-slide with a medium 

 denser than air. 



The usefulness of this apparatus has 

 been recognized by all who have be- 

 came familiar with its use, and it is 

 not only employed as an ordinary ac- 

 cessory, occasionally, but as a constant 

 auxiliary in daily ajDpIication. 

 o ■ 



New (Centering Turn-table. 



The turn-table represented in Fig. 

 4 is the invention of Mr. Joseph 

 Zentmayer, of Philadelphia, and it 



The plan of centering the slide is 

 quite original and perfect in its results. 

 The slide is placed so that its edges 

 are in contact with the two pins pro- 

 jecting from the face of the plate. A 

 ring with an oval inner edge is fitted 

 to the periphery of the disk, in such 

 a way that by turning it the slide is 

 grasped at the diagonally opposite 

 corners by the inner edge of the ring, 

 and is thus centered longitudinally. 

 The two pins centre it the other way. 



The ring may be easily removed, 

 and spring clips substituted when de- 

 sirable. 



The figure will afford a better idea 

 of the device than can be given by 

 words. The price of the turn-tablfe 

 is $5.00. 



Next month we shall describe an- 

 other of Mr. Zentmayer's improve- 

 ments, which is a new form of de- 

 taching nose-piece, the number of 

 which is rapidly increasing. 



Fig. 4. — Zentmayer Centering 



needs no words of ours in its favor 

 when the maker is so well known, for 

 nothing that is not mechanically ex- 

 cellent has ever come from Mr. Zent- 

 mayer's hands. 



Adulteration of Lard. 



Dr. W. T. Belfield describes his 

 method of detecting tallow in lard by 

 the microscope in the Proc. Am. Soc. 

 Mic. The process is as follows : — 



Ten grains of the material to be ex- 

 amined are dissolved in two drachms 



of Squil)b's 

 ether, in an 

 open test- 

 tube. As 

 the ether 

 evaporates, 

 crystals are 

 deposited. 

 These may 

 be examin- 

 ed in the 

 etherial so- 

 lution, but 

 it is better 

 to pour off 

 the mother 

 liquor and wash the crystals once or 

 twice with clean ether. By thus ex- 

 amining the crystals under the micro- 

 scope pure lard will show thin, rhom- 

 boidal plates, the obtuse angles gf 



Turn-table. 



