408 Ohituary. 



•Czapski became head of the Carl Zeiss Stiftung as his chosen 

 successor. 



The chief scientific work from the pen of Dr. Czapski was his 

 " Foundation of the Theory of Optical Instruments after Abbe," * 

 rwhich first appeared as part of Winkelmann's Handbuch der 

 Physik in 1893. A second enlarged and amplified edition was 

 published in 1904. This work, whilst giving a complete and con- 

 sistent theory covering the whole ground from the standpoint of 

 geometric optics, deals fully with the new modes of treatment of 

 the subject introduced by Abbe, purposely omitting, however, the 

 consideration of instruments and matters which in the author's 

 opinion had already been dealt with comprehensively and adequately 

 by others. 



Owing to the absence of any English translation of this 

 masterly contribution to the science of optics, its full value has 

 scarcely yet been recognised. It is safe to predict that as it 

 becomes better known its value will become more fully appreciated. 



A few words from the preface of the book, which undoubtedly 

 contains a deal of original work also on the part of Czapski, may 

 serve to illustrate the natural modesty and innate sense of fairness 

 of the man : — " The contents are essentially the product of Abbe's 

 mind. But as regards the presentment of the subject, though I 

 have been in constant intercourse with my honoured friend and 

 teacher, the trend of circumstances has scarcely permitted us to 

 more than discuss the general outline of the work. Whilst, there- 

 fore, I must take full responsibility for the correctness and proper 

 presentment of the subject, I must disclaim all merit for the matter 

 itself." 



A book based upon Czapski's work referred to above, and 

 entitled " Image Formation in Optical Instruments from the stand- 

 point of Geometric Optics," has also appeared in 1904, of which 

 parts have been written by Dr. Czapski, in collaboration with other 

 members of the scientific staff of Carl Zeiss. f 



Apart from his book. Dr. Czapski wrote a number of other optical 

 papers of a varied character from time to time. An interesting 

 study on the Limitations of the Microscope issued from his pen in 

 1891,$ in which he compares the theories of Helmholtz and Abbe, 

 treats of the difficulties connected with increasing the N.A. of 



* " Grundziige der Theorie der Optischen Instrumente nach Abbe." Published 

 by Johanu Anibrosius Barth, Leipzig ; 1st. ed., 1893, 2nd ed., 1904. Both editions 

 have been published separately, as well as in Winkelmann's Handbuch. 



t " Die Theorie der Optischen Instrumente. I. Die Bildererzeugung in Opti- 

 schen Instrumenten," edited by M. von Rohr, published by Julius Springer, 

 Berlin, 1904. 



X " Die voraussichtlichen Grenzen der Leistungsfahigkeit des Mikroskops." 

 Zeitschr. wiss. Mikrosk., viii. (1891) pp. 145-55. See also article on " The Future 

 of the IMicroscope," by Czapski, pp. 357-64, in Van Heurck's book on the Micro- 

 scope, English edition by Wynne E. Baxter, published by Crosby, Lockwood, 

 -and Son, London 1893. See also this Journal, 1891, pp. 814-18. 



