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It was Feil, a son-in-law or near relative, who made the glass from which Clark fabricated the lenses of the great telescope of the Lick Observatory. His successor, Mantois, of Paris, carried the art to a point of perfection never before approached.
Every part of the immense observatory and of the telescope is of American production, with the single important exception of the cast glass disc from which the two principal lenses, the one double convex and the other plano-concave, are produced. These were cast by Mantois, of Paris, whose superiority to the American manufacturers of optical glass is recognized.
At the glass foundry of Mantois, of Paris, the finest and largest discs ever produced in the world are cast. But after the castings are made they are sent to America, to be made into those wonderful objectives which constitute the glory of the apparatus upon which the New Astronomy relies for its achievements.
They had been cast by Mantois for the University of Southern California, when the erection of a great observatory on Wilson's Peak was under consideration. In the Clark workshop they were combined into a superb objective, brought to perfection by trials and delicate touches extending over nearly five years.
This proved to be a very difficult task. Chance & Co. were unwilling to undertake the work and Feil had gone out of business, leaving the manufacture in the hands of his son. The latter also failed, and the father had to return. Ultimately the establishment was purchased by Mantois, whose success was remarkable.
Passing now from these large reflectors to refractors, further improvements have been made in the manufacture of glass by Chance, of Birmingham, Feil and Mantois, of Paris, and Schott, of Jena; while specialists in grinding lenses, like Alvan Clark, of the U.S.A., and others, have produced many large refractors.
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