C. A. Steinheil Solme, Miinchen. 103 



No. 2792. 



C. A. Steinheil Sohne, Miinchen. 



Optical and Astronomical Works. 



Dimensions are stated in terms of the metric system and of the old duodecimal 



French' measure. 



This establishment was founded in 1855 by the physicist Charles 

 Augustus von Steinheil, Council of Ministry and Ordinary Member 

 of the Academy of Sciences, and by his son Dr. Adolphus Steinheil, 

 at the instigation of King Maximilian II. of Bavaria, who wished to 

 perpetuate the reputation which Fraunhofer had won for the town of 

 Munich by his achievements in optical science. 



In 1865 the former retired from business and his son entered into 

 partnership with his brother Edward Steinheil and established the 

 IIOAV still existing firm of C. A. Steinheil Sohne. 



Charles Augustus von Steinheil died in 1870 (14. Sept.). 

 Eight years later Edward Steinheil received a sunstroke on a 

 voyage to Columbia and died in the port of St. Thomas. 



The present heads of the firm are: Dr. Adolphus Steinheil, 

 the son of the founder, extraordinary Member of the Academy of Sciences, 

 and, since 1889, his son Dr. Eudolph Steinheil. 



From the commencement the practical manufacture of optical com- 

 binations was based upon precursory extensive and exhaustive com- 

 putation of all optical data which were necessary for their systematic 

 production and an equally methodical system of testing served for cor- 

 rectly controlling each separate stage of their manufacture. 



The following are the tests which are implied by correct and 

 systematic manufacture : 



1. Critical selection of the glasses according to their chemical 

 and optical properties; 



2. Determination of the properties of the glasses independently 

 of the data supplied by their makers; 



3. Examination of the glasses with respect to defects which may 

 affect the combinations optically or esthetically ; 



4. Calculation of the prisms and the systems of lenses so as to 

 completely determine, by pure calculation, all the elements of 

 the optical combination, (cf. ,.Handbuch der angeivandten Optik", ty 

 Dr. Ad. Steinheil and Dr. Ernst Voit, Leipzic, Teubner, 1891); 



5. Measurement, by means of the spherometer constructed in 1845 

 by C. A. von Steinheil of the radius found by mechanical 

 means. 



