Lalande several discs of flawless crystal
four to six inches in diameter. Lalande advised him to keep his secret,
but in 1805 he was induced to remove to Munich, where he became the
instructor of the immortal Fraunhofer. His return to Les Brenets in 1814
was signalised by the discovery of an ingenious mode of removing
striated portions of glass by breaking and re-soldering the product of
each melting, and he eventually attained to the manufacture of perfect
discs up to 18 inches in diameter. An object-glass for which he had
furnished the material to Cauchoix, procured him, in 1823, a royal
invitation to settle in Paris; but he was no longer equal to the change,
and died at the scene of his labours, February 13 following.

This same lens (12 inches across) was afterwards purchased by Sir James
South, and the first observation made with it, February 13, 1830,
disclosed to Sir John Herschel the sixth minute star in the central
group of the Orion nebula, known as the "trapezium."[315] Bequeathed by
South to Trinity College, Dublin, it was employed at the Dunsink
Observatory by Bruennow and Ball in their investigations of stellar
parallax. A still larger objective (of nearly 14 inches) made of
Guinand's glass was secured in Paris, about the same time, by Mr. Edward
Cooper of Markree Castle, Ireland. The peculiarity of the method
discovered at Les Brenets resided in the manipulation, not in the
quality of the ingredients; the secret, that is to say, was not
chemical, but mechanical.[316] It was communicated by Henry Guinand (a
son of the inventor) to Bontemps, one of the directors of the glassworks
at Choisy-le-Roi, and by him transmitted to Messrs. Chance of
Birmingham, with whom he entered into partnership when the revolutionary
troubles of 1848 obliged him to quit his native country. The celebrated
American opticians, Alvan Clark & Sons, derived from the Birmingham firm
the materials for some of their early telescopes, notably the 19-inch
Chicago and 26-inch Washington equatoreals; but the discs for the great
Lick refractor, and others shaped by them in recent years, have been
supplied by Feil of Paris.

Two distinguished amateurs, meanwhile, were preparing to reassert on
behalf of reflecting instruments their claim to the place of honour in
the van of astronomical discovery. Of Mr. Lassell's specula something
has already been said.[317] They were composed of an alloy of copper and
tin, with a minute proportion of arseni