ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 113 



rays on the observer's eye are parallel, and there is therefore no error due 

 to parallax. 



The Collected Treatises of Abbe.* — Dr. S. Czapski has undertaken 

 the welcome task of collecting and publishing in a compact form the 

 various treatises of Prof. Abbe. This, the first volume, is to be followed, 

 in due course, by two or three others, all on mathematical and optical 

 subjects ; and a later volume will contain his writings on social and 

 economical topics. 



The order adopted is chronological, and treatises originally written 

 in other languages have been translated into German. The task of 

 editing has been performed by Prof. Ambronn. 



The following is a translation of the titles of the various papers, and 

 the reference is given when the original was in English. The year of 

 composition is also given. 



1. On a spectrum apparatus for the Microscope (1870). 



2. On the determination of the light-intensity of optical instruments, 



with especial reference to the Microscope, and apparatus for 

 light concentration (1871). 



3. Contributions to the Theory of the Microscope and of microscopical 



veracity (1873). 



4. On a new illuminating apparatus for the Microscope (1873). 



5. Description of the apertometer (1877 ).f 



6. The optical auxiliaries of the Microscope (1878). 



7. On micrometric measurement by means of optical images (1878). 



8. On the computation of blood corpuscles (1878). 



0. On Stephenson's system of homogeneous immersion for Microscope 

 objectives (1879). 



10. On new methods for improving spherical correction applied to the 



construction of wide-angled object-glasses (1879)4 



11. On the conditions of aplanatism of lens-systems (1879). 



12. Some remarks on the apertometer (1880). § 



13. Description of a new stereoscopic ocular, with general remarks on 



the conditions of micro-stereoscopic observation (1880). 



14. On the limits of geometrical optics, with observations on Altmanu's 



treatise ' On the Theory of Image-formation ' (1880). 



15. On the conditions of orthoscopic and pseudoscopic effects in the 



binocular Microscope (1881). j| 



16. On the estimation of aperture in the Microscope (1881). If 



17. The relation of aperture and power in the Microscope (1882).** 



18. On the mode of vision with objectives of wide aperture (1882).ff 



19. Note on the proper definition of the amplifying power of a lens or 



a lens-system (1884)4$ 



* Gesnrnmelte Abhandlungen,von Ernst Abbe, Erstcr Band, 48G pp., "_' pis , 29 figs. 

 Portrait of author. Published by Fischer, Jena, 1904. 



t Journal R.M.S., i. (1S78) pp. 19-22. 



% Op. cit., ii. (1879) pp. S12-24. § Op. cit., iii. (1SS3) pp. 20-31. 



|| < >p. Pit., i. (1881) pp. 203-11. i Op. cit., i. (1881) pp. 38&-12 i. 



** Op. cit., ii. (1882) pp. 300-9, 4G0-73 ; iii. (1883) pp. 790-S12. 

 tt Op. cit. iv. (1884) pp. 20-2G. }$ Op. cit, iv. (1881) pp. 348-51. 



Feb. 17th, 1904 i 



