452 The Achromatic Telescope. 



deterioration in performance.* DolloncFs formulas were not 

 made public ; and the attempts which were made in France to 

 imitate his object-glasses mechanically proved, as might be 

 expected, failures ; great pains were taken in investigating the 

 theory by the most okilful continental mathematicians, and 

 Clairaut and D^Alembert devised elaborate formulas ; but these 

 had not much success in practice, so that the manufacture was 

 long retained in England by Dollond/s successors, and by 

 Tulley, though on what would now be considered a diminutive 

 scale, from the impossibility of getting large discs of 

 homogeneous glass. At length a fresh impulse was given to 

 the manufacture by the celebrated German, Frauenkofer ; and 

 the Munich Optical Institute, under his superintendence, long 

 surpassed every similar establishment, till of late years the 

 successful practice of this most delicate species of workman- 

 ship has been extended to various parts of the world. The 

 career of Frauenhofer was so remarkable that we pause a 

 moment, in our description, for the purpose of narrating its 

 most interesting facts. This extraordinary man was born in 

 Bavaria, in the year 1787, in a humble condition of life, and 

 being left an orphan, would have been destined to the lathe 

 but for the weakness of his frame. When 14 years of age, 

 while apprenticed to a glass-worker at Munich, he was buried 

 for four hours in the ruins of a house, whence he was extri- 

 cated under the superintendence of King Maximilian ; and to 

 this apparently accidental but really providential occurrence, 

 he was inde"bted for a patron whose generosity delivered him 

 from a severe master, who denied him the use of books and 

 candle, as well as for a friend, Counsellor Utzschneider, the 

 future partner of his great optical undertaking. Though his 

 education had been so neglected that he was scarcely able to 

 write, he became a diligent student of mathematics, and not- 

 withstanding the pressure of poverty, from which he tried in 

 vain to escape by engraving visiting cards, he devoted much 

 time to grinding and polishing lenses. On the formation of 

 an establishment at Benedictbauern, near Munich, for the 

 fabrication of optical instruments, in which Utzschneider was 

 a partner, the need of good glass became so apparent, that it 

 was determined to manufacture it upon the spot, and for this 

 purpose, the celebrated Louis Guinand was brought from 

 Brenetz, in the Jura Mountains, where he had been very suc- 

 cessful in casting flint glass. Skilful workmen were also 

 needed ; and after much reluctance in applying, from an 

 impression that Utzschneider had forgotten him, Frauenhofer 

 obtained the post of second optician; this was about thoyi 



* The triple const ruction is. said to liaTe been revived of lata in Italy by 

 Amici, from formula) by Mossotti, with remarkable success. 



