696 



SUMMARY OF CUREENT RESEARCHES RELATING TO 



C3) Illuminating' and other Apparatus. 

 Taylor's Oleomargariseope.* — During the prosecution for violation 

 of the Butter Laws of the District of Columbia, it was found necessary 

 in jury trials to have a simpler form of microscopic and polariscopic 



combination than the cumbrous stand. 

 Fig. 89. Fig. 90. with polariscope, in general use, 



since each of the parties interested 

 — ^judge, jurymen, and attorneys — ■ 

 desired to see for themselves the 

 crystalline forms seen in the fatty 

 compounds known as oleomargarine. 

 To this end Dr. J. Taylor contrived 

 the oleomargariseope, illustrated by 

 the accompanying figs. 89 and 90. 



Fig. 89 represents its general 

 appearance when not in use. Fig. 

 90 represents a sectional drawing 

 showing its internal structure. 



A, an ordinary eye-piece. 



B, a 1/2 in. objective of the 

 usual constructiou. 



a, Nicol's prism or analyser. 



h, polarizer firmly secured in 

 tube c, which tube may be rotated 

 as desired, thereby changing the 

 prismatic colours. 



d, two discs of thin plate glass, 

 between which a small portion of 

 butter or oleomargarine is placed, 

 the discs held in position by ring/. 



e, a disc of selenite held in posi- 

 "^ tion by ring g. 



h, a lens for the double purpose of illuminating the polarizer and 

 protecting it from dust. 



A lens is also placed over and above the polarizer h, which concen- 

 trates the light on the object between the discs d. 



It will be seen from the drawing that the objective is readily focused 

 by means of the draw-tube. 



When the object is held up to a strong light, if the butter is pure 

 and free from adulteration, an even green or red colour only will be 

 observed, depending upon the character of the selenite used. If " oleo " 

 or lard is used instead of pure butter, a fine display of prismatic colours 

 will be observed. 



Recent Improvements in Electric Lighting applied to Micrography 

 and Photomicrography.t — Dr. H. van Heurck describes the Radiguet 

 battery and electric lamp of Prof. Engelmaun, a combination very service- 

 able for the microscopist, since it affords a bright light whose intensity 

 is under perfect control, and the cost of maintenance is very trifling. 



Each element of the Eadiguet battery comprises a stoneware jar, a 

 carbon cylinder, a porous pot, and an amalgamating support with its 



* Proc. Amer. Soc. Micr., x. (1888) pp. 159-60 (2 figs.), 

 t Bull. Soc. Belg. Micr., xv. (1889) pp. 24-31 (4 figs.). 



