546 SUMMARY OF CURRENT RESEARCHES RELATING TO 



eccentrically at It and are not seen in the telescope at E. They may, 

 however, he seen in an auxiliary telescope pointed in the line R, and they 

 then facilitate the adjustments. Rays diffracted at the angle Li, how- 

 ever, are respectively transmitted and reflected hy M and interfere in 



Fig. 66. 



the telescope in the line E. Similarly, rays diffracted at an angle 0' > i 

 interfere in the line D. 



The author describes the adjustments necessary, and several modifi- 

 cations of the experiment. 



Hartik g, H. — Uber erne Grenzbedingung bis der Konstruktion gewissen optischer 

 Systeme. 



[The author has worked out the numerical values of the co-efficients for 

 certain two-lens optical systems.] 



Zeit. f. Instrumentenk., xxx. (1910) pp. 359-63. 



Heinrich, K.— Verwendung der Savartschen Platte bei der Beobachtung der 

 relativen Phasendifferenz zur Bestimmung der optiscben Konstanten von 

 Metallen. 



Berichte fiber die Verli. d. KSnig. Sachsischen Gcsell. d. Wissenscliaften 

 zu Leipzig, Math.-Phys. Klasse, v. (1910) pp. 253-5. 



(6) Miscellaneous. 



Quekett Microscopical Club.— The 474th Ordinary Meeting was 

 held on May 28, Dr. E. J. Spitta, F.R.A.S., Vice-President, in the Chair. 

 Mr. 0. 1). Soar, F.L.S. F.R.M.S., read a paper on "The Work of the 

 late Saville Kent on British Hydrachnids." Together with Mr. William- 

 son, of Edinburgh, the author is preparing a monograph of British 

 Hydrachnids, and having, by courtesy of the British Museum authori- 

 ties, had access to Saville Kent's collection of slides, notes, and draw- 

 ings, it was thought a brief account would be of interest to the Club. 

 Saville Kent's work on these organisms was begun in 1867 and continued 

 till 1883, and from the material available Mr. Soar had identified fifty 



