1082 SUMMARY OF CUBRENT RESEARCHES RELATING TO 



disease, but with health as well, and that they, acting in the pores of the 

 human system as workers, carry off the sewage of the system, and thus 

 overcome the effects of violations of nature's laws, and thus work to the 

 end of aiding man in working out in himself the theory of the survival of 

 the fittest. He said that microscopy has a great work to do in geology, 

 and thus in affecting the commerce of the world."] 



Amer. Mon. Micr. Journ., VI. (1885) pp. 166-7. 



Smith, H. L. — Device for Testing Eefractive Index. \_Supra, p. 1066.] 



Ibid., pp. 181-2 (1 fig.). 

 Cf. Queen's Mkr. Bull, II. (1885) p. 40. 

 SoRBT, H. C— See Wedding, H. 

 W., E. D. — Measurement of Power and Aperture of Microscopic Objectives. 



[1. Describes the following method : — Kemove the eye-piece ; adjust the 

 length of the tube by means of the draw-tube to exactly 10 in. from the 

 back lens of the objective (this may conveniently be done by dropping a 

 straw cut to 10 in. in length into the tube, allowing the lower end of it to 

 rest on the back lens). Place a stage-micrometer divided into hundredths 

 and thousandths of an inch on the stage. Hold a finely groimd slip of 

 glass on the top of the draw-tube. Focus until the divisions of the stage- 

 micrometer are clearly visible on the ground-glass slip, when they can be 

 marked on the slip with a pencil. The extent to which the divisions of 

 the micrometer are magnified on the glass slip indicates the power of the 

 objective. «■ 



2. Also gives a method for ascertaining the angular aperture of an 

 objective: — Place the Microscope with its tube in a vertical position on 

 a table having a dark-coloured cover. Take out the eye-piece. Kack 

 down the tube until the front of the objective is level with or below the 

 under side of the stage. All substage fittings must be removed. Take 

 two pieces of white card and place them on the table right and left of the 

 Microscope. Look dowii the tiibe, and move the pieces of card until you 

 can just see the extreme edge of each piece of card mirrored on each side 

 of the field of the objective on the extreme edge of the circle of the field. 

 Now measure the distance apart of the two pieces of card (their inside 

 edges) and the distance from the table of the front lens of the objective. 

 Draw the first-mentioned distance on a sheet of paper as a horizontal 

 line, and set up the latter distance from the middle of this line, and per- 

 pendicular to it. Draw two lines from the ends of the horizontal distance 

 to the top of the perpendicular one — when the angle formed by these two 

 lines will be the angular aperture of the objective, or a close approxima- 

 tion to it.] 



Engl. Mech., XLII. (1885) pp. 100-1. 

 Ward, R. H. — Choice of Objectives and Oculars. 



[" It is probably quite safe to say that objectives anywhere from 1/8 in. to 

 1/12 in., if not lower, can now be obtained, which will show as well as 

 has ever been done anything that has yet been seen by the Microscope. 

 The question as to the choice of moderate or extreme apertures for ob- 

 jectives is still open, and somewhat evenly disputed." "In the com- 

 bining of oculars with objectives it is still undecided whether it is 

 preferable to secure a sufficient variety of powers by means of a large 

 number of objectives, or by the high and low eye-piecing of a few."] 



Journ. N. York Micr. Soc, I. (1885) p. 164, 

 from article " Microscopy," in ' Appleton's Annual Cyclopedia ' for 1884. 

 ,, „ The Binocular. (^Concluded.) 



[Wenham's, Nachet's, and Abbe's, and general remarks.] 



Queen's Micr. Bull, II. (1885) p. 38, 

 from The Microscope in Botany (Behrens). 

 Wedding, H. — The properties of malleable Iron deduced from its microscopic 

 structure. 



[Includes a letter from Dr. H. C. Sorby, on a " Direct illuminative " con- 

 trived by him. Post.'] 



Colliery Guardian, 18S5, June 5, p. 908. 



