582 SUMMARY OF CURRENT RESEARCHES RELATING TO 



balsam must be resoftened by placing it for a few m inutes on the stove, 

 and the operation repeated with greater care. 



Anonymous — Praktische Arbeitserfahrungen in der Photographic (Mikrophoto- 

 graphie). Zeitschr. angew. MUcr., x. (1904) p. 24. 



Leiss. C. — Ueber eine neue Camera zur stereoskopischen Abbildung mikroskopischer 

 und makroskopischer Objecte. Zeitschr. Instrumentenk., xxiv. (1904), p. 61 ; 



Zeitschr. Krystallug. u. Mineral, xxxviii. (1903) p. 99. 



(£) Microscopical Optics and Manipulation. 



Chabkie, C. — Sur la fonction qui represente le grossissement des objets vus a 

 travers un cone de cristal. Comptes Rendus, exxxviii. (1904) p. 349. 



D oku lid, Tif. — Die Bestimmung der optischen Constanten eines centrirten spha- 

 rischen Systems mit dem pracisionsfocometer. 



Der Mechaniker, xii. (1904) p. 37. 



Everett, J. D.— On skew refraction through a lens; and on the hollow pencil 

 given by an annulus of a very obliquely-placed lens. 



Proc. Roy. Soc, lxxi. (1903) p. 59. 



,, „ On the resolving power in the Microscope and Telescope. 



Rep. British Assoc, Glasgow, 1901, p. 569. 



Kletber, J. — Astigmatismus bei Hohlspiegeln. 



Zeitschr. Unlerr., xvi. (1903) p. 208. 



Mace de Lepinay, J., & H. Buissox — TJeber eine neue Methode der optischen 

 Dickenmessung. Zeitschr. Instrumentenk., xxiv. (1904) p. 30 ; 



Comptes Rendus, exxxv. (1902) p. 283. 



Anonymous — Ueber die Grenzen der mikroskopischen Abbildung und die Sichtbar- 

 machung " ultra mikroskopischer." Theilchen. 



[After referring to Abbe's theorems on the limits of visibility, the writer 

 describes tbe experiments of Siedentopf and Zsigmondy, which have been 

 more than once described in our Journal.] 



Central-Zeit. f. Opt. u. Mech., xxv. (March 1, 1904) 



pp. 51-3 (3 figs.) 



(6) Miscellaneous. 



Optical Bench.* — The firm of R. and J. Beck manufacture an 

 optical bench and appliances for Microscope illumination, photomicro- 

 graphy, micro-projection, and optical lantern projection. It consists of 

 a table (fig. 83), having a rigid iron framework and a wooden top, 

 54 in. by 20 in., which supports the optical bench, the Microscope and 

 the illuminant. It runs on four castors, by the side of which are screw 

 pillars with lock-nuts, by which the castors may be raised off the 

 ground. The bench proper is a steel rail 80 in. long, with a prismatic 

 section ; this is carried on two cross bars, at the ends of which are four 

 screwed pillars with milled heads and clamp nuts, the ends of which fit 

 into sockets fixed upon the wooden table. By means of the pillars the 

 rails may be raised or lowered. Along the dove-tailed rail the various 

 pieces of apparatus slide with a spring fitting, and may be clamped in 



* R. & J. Beck's Special Catalogue, 1904(12 figs.). 



