Page:History of the Royal Astronomical Society (1923).djvu/130

 io8 HISTORY OF THE [1840-50 be found out one by one, composition, support, illumination, per- sonality ; and the matter passes out of the decade unconcluded. Glass. The Council in 1846 February, " cannot but mention what is one of the most remarkable events of the year, though perhaps no one of the parties concerned in it gave our science a thought. They allude to the repeal of the excise duty on glass, which might be called with perfect truth an astronomical window tax. The regulations up to then rendered experiments for the improvement of optical glass almost impracticable, and a great deal too expensive. It may now be confidently hoped that in a few years our country will not be obliged to admit that we are surpassed by foreigners in this particular." The difficulty was very real. Simms was unable to secure the flint glass to make the Liverpool equatoreal (8-inch), and the whole was ordered from Merz, of Munich. The same artist had supplied the 15" O.G. for Cambridge, U.S., and 12" for Cincinnati. Later on, however, Simms succeeded in making an 8" O.G. (12' 6" focus) for the new Greenwich transit circle, which satisfied Airy's tests it separated 77 Coronse (o"-6) but failed at y Coronae (o"'4). The price was 275 ; where the glass was obtained is not stated. Soon after he was. able to announce that the difficulty was at an end (1849 April) " the firm of Chance & Co., of Birmingham, with the assistance of a foreign artist, have succeeded in manufacturing flint glass for optical purposes by no means inferior, so far as my trials enable me to judge, to the very best that was formerly pre- pared by the elder Guinand." This foreign artist was H. Bon- temps, whom the troubles in Europe in 1848 had driven from Choisy-le-Roi, and to whom the younger Guinand had communi- cated the method that had made his father's, and Fraunhofer's, and Merz and Mahler's fame, of stirring the melted glass till it could be stirred no longer, and then chilling the pot somewhat quickly, by which the melted mass split itself into blocks, each sensibly homogeneous. Eclipses. There are numerous eclipse observations within our period ; mostly they are filled up with the tedium of Baily's Beads, but there is a notable exception. In 1842 a total eclipse of the sun took place in North Italy and Austria. Baily and Airy saw it, the former from Pavia, the latter near Turin. Both sent vivid accounts ; Airy's in particular is tremendous, and quite outdoes the reality of most experiences. But what matters is, that both record and draw the pink " protuberances " then noted for the first time. Solar Physics. There was no physics of the sun in this period ; Schwabe's announcement of the sun-spot period in 1844 in Astr. Nach. seemingly attracted no one's attention, or at least