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 ii s. ix. APRIL is, 1914.] NOTES AND QUERIES.

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was not the real inventor, and that such telescopes had been made twenty-five years before the granting of his patent by Mr. Moor Hall. John Dollond, to whom the Copley Medal of the Royal Society had been given for his invention, was then dead, and his son brought an action for infringing the patent against Champness. There is no report of the case, but the facts are referred to in the reports of subsequent cases. It appears that workmen who had been employed by Mr. Moor Hall were examined, and proved that they had made achromatic object-glasses as early as 1733. Dollond's patent was not set aside, though the evidence with regard to the prior manufacture was accepted by Lord Mansfield, who tried the case, as having been satisfactorily proved .... Mr. Hall was a bencher of the Inner Temple, and was alive at the time of the action. He was a man of some property, and is spoken of on his tombstone as an excellent lawyer and mathe- matician. He was not a Fellow of the Royal Society, but must certainly have known of the gift of the Copley Medal to Dollond. It is very curious the conflicting evidence we have to recon- cile, but I think the balance of evidence is in favour of there having been a prior invention of achromatic object-glasses before the date of Dollond's patent." Astron. Register, 1886; see also The Observatory, 1886.

Hall resided, at New Hall, Sutton, Essex, where he died 17 March, 1771, aged 67. His elder sister Martha Hall put up a. marble monument to him in Sutton Church, denning him as a judicious lawyer, an able mathema- tician, a polite scholar, a sincere friend, and a magistrate of the strictest integrity. Hall's autograph is suspended in the Council room of the Royal Astronomical Society.

Pierre Louis Guinand is referred to by Sir David Gill in ' Ency. Brit.' (article ' Tele- scope ') ; but there was a contemporary book about him in English : ' ' Some Account of the late M. Guinand and of the Discovery made by him in the Manufacture of Flint Glass for Large Telescopes. By E. R. 1825." There is a good biography of him in the ' Grand Dictionnaire Larousse ' and in Hoefer's ' Biographie Universelle. ' The secret of Guinand's methods was, I believe, conveyed after his death to the eminent firm of Chance Brothers of Birmingham, the makers of large disks of optical glass.

Heavy duties were levied on glass in the seventeenth century, and the glassmakers petitioned in 1695-7 continually to have these duties removed. There are numerous single- sheet petitions in the B.M. The information which MB. OWEN is seeking as to taxes on glass will no doubt be found in the Report f Commissioners of Excise Inquiry on the Duties on Glass, 1835. This report has historical notices with references to glass, and papers on various branches of the glass trade. A. L. HUMPHREYS.

187, Piccadilly, W.

An interesting article on the giant tele- scope at the Paris Exhibition of 1900 appeared in Pearson's Magazine for May, 1900, in which the process of making glass for optical purposes is described. The lenses are there stated to have been made by M. Mantois of Paris, the direct successor of Guinand.

I have before me a price-list of Chance Brothers & Co., Soho, Birmingham, of April, 1880, of their Optical Glass for Astronomical Purposes, in which it is stated that

" the process by which our optical glass is manu- factured is that which was first introduced by Guinand of Solothurn, in Switzerland."

In the ' Imperial Dictionary of Universal Biography ' there is a short notice of Pierre Louis Guinand (born in 1748, died 1824) referred to in Chance's price-list. I believe that the ingredients or, at all events, their proportions are a trade secret, no patent ever having been taken out.

There is a large number of works under the heading of ' Glass and Glass-making,' in English, French, and German, in the library of the Patent Office, London. The list is too long to give here, but the Catalogue can be obtained for 6d. It is No. 2 of that Library's series. E. A. FRY.

227, Strand, W.C.

Perhaps the following may prove useful to your correspondent inquiring re the above : -

"Salvino degli Armatihad invented a process for making glass of a lenticular shape, and Bacon took up this invention, and, having perfected it, made achromatic glasses and the telescope." Lacroix, 'Science and Literature in the Middle Ages,' p. 180.

Perhaps some of the following works might contain further information :

'On the Nature and Physical History of Glass and its Applications in Practical Chemistry.' E. W. Brayley. 1845.

'Manufacture of Glass for Optical Purposes/ M. Faraday. Trans Royal Soc., vol. cxx. 1830.

'Theorie und Geschichte der photographischen Objektivs.' M. v. Rohr. Berlin, 1899.

There are preserved in the vestry of All Saints' Church, Pavement, York, two lenses which were formerly in the lantern in the tower of the church, which was lighted to guide travellers through the Forest of Galtres towards the city. They are at present mounted in a frame close to the wall, and appear, as nearly as can be judged, to be double convex, about eight inches in diameter, and to have turned " anbittie " in the making. JOHN A. KNOWLES.