THE AMERICAN 



MONTHLY 



MICROSCOPICAL JOURNAL. 



Vol. X. MARCH, 1889. No. 3. 



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The Making of Apocliromatics. 



By ROMYN HITCHCOCK. 



Jena is situated about three hours by rail from Leipzig, but to get 

 there one must change cars twice. We arrived there at 8 o'clock on 

 the 13th of December, and were most cordially welcomed by Professor 

 Dr. Abbe, whom we found awaiting us at the station. In a few min- 

 utes we were in very comfortable quarters at the Hotel zum schwartzen 

 Baren, on Luther Place, where Luther was several times a guest. We 

 visited many places of interest in the old town w r ith Dr. and Mrs. Abbe, 

 among others the houses once occupied by Schiller and Gothe. In the 

 garden of the Schiller house, until lately Dr. Abbe's home, a stone slab 

 marks the spot where stood a summer-house in which the poet wrote 

 his Wallenstein, and near by a stone table over which he and Gothe en- 

 joyed many a talk. The town has many old monuments of the past, 

 but it has lost much of its former, importance. It dates from the twelfth 

 century. The University was founded in the time of the Reformation, 

 and during the last century it had a large number of students. The 

 average number now is about six hundred. 



On Monday morning I went to Mr. Zeiss' establishment, and Dr. R. 

 Zeiss, who succeeds his father in the business, conducted me through 

 the works. Although some of the methods in use at this place differ 

 from those employed elsewhere, and although the excellence and accu- 

 racy of the work is rendered possible only by the application of such 

 methods, nothing is concealed from the visitor. As Dr. Zeiss says, they 

 have no secrets. The brass work is clone by machinery of the best kind, 

 much of it specially made fo.r the purpose, as, for instance, the ingenious 

 device for cutting the diagonal rack-work for moving the body-tube. 

 The rack is of brass, but the pinion wheel is steel. Brass polishing is 

 done, as usual, with French emery, but I was much interested to learn 

 that the dead black portions, such as the stages and other parts, are 

 made black by grinding with emery powder. This may be the usual, 

 or, at least, a very common method, but I have always been under the 



Copyright, 1889, by C. W. Smiiey. 



