ERA OF NEWTON, HALLEY, AND HEfcSCHEL. 45 



far more remote, and reasonably suppose the star which presents the faintest pencil 1 

 of light to the eye to be at least twice or thrice the distance of Sirius. Yet onwards,. 

 192 times further, the space-penetrating power of the telescope at Slough swept the 

 heavens. It was completed in the year 1789, but the frame of the instrument be- 

 coming decayed through exposure to the weather, it was taken down by Sir John Herschel 

 in 1823v 



It will be convenient here to notice a reflecting telescope of far greater magnitude and 

 power, recently constructed by the Earl of Rosse, and now in use at the seat of that 

 nobleman, Birr Castle, in Ireland. The mechanical difficulties involved in this work 

 the patience, perseverance, and talent required to overcome them and the great expen- 

 diture necessarily incurred render the successful completion of this instrument one of 

 the most extraordinary accomplishments of modern times ; and entitle its owner and! 

 projector, from first to last, to the admiration of his countrymen. When the mechanical 

 skill and profound mathematical knowledge essential to produce such a work are duty 

 considered, together with the years devoted to previous experimenting, and an outlay of 

 upwards of twelve thousand pounds, this telescope must be regarded as one of the most 

 remarkable and splendid offerings ever laid upon the altar of science. The speculum ha 

 a diameter of six feet, and therefore an area of reflecting surface nearly four times greater 

 than that of the Herschelian, and its weight approaches to four tons. The casting a 

 work of no ordinary interest and difficulty took place on the 13th of April, 1842, at nine 

 in the evening ; and as the crucibles poured forth their glowing contents a burning 

 mass of fluid matter, hissing, heaving, and pitching for the moment almost every one 

 was anxious and fearful of accident or failure but Lord Rosse, who was observed direct- 

 ing his men as collectedly as on one of the ordinary occurrences of life. The speculum 

 has been formed into a telescope of fifty feet focal length, and is established between two 

 walls of castellated architecture, against one of which the tube bears when in the meridian. 

 It is no slight triumph of ingenuity, that this enormous instrument may be moved about 

 and regulated by one man's arm with perfect ease and certainty. What will result from 

 its application to the heavens remains to be ascertained, but an advancement of sidereal 

 astronomy may be confidently anticipated. 



To return to Herschel. No addition had been made of any new body to the universe 

 since Cassini discovered a fifth satellite in the train of Saturn. Nearly a century had elapsed 

 without any farther progress of that kind. The solar system, including the planets, satel- 

 lites, and Halley's comet, consisted of eighteen bodies when Herschel turned his attention 

 to astronomy ; but, before his career of observation terminated, he increased the number 

 to twenty-seven, thus making the system half as large again as he found it, as to the 

 number of its constituents a brilliant recompence, but not an over-payment, considering 

 the immense expenditure of time, and toil, and care. A primary planet with six moons, 

 and two more satellites about Saturn, composed the reward. It was on the 13th of 

 March, 1781, that, turning a telescope of high magnifying power though not his 

 gigantic instrument to the constellation Gemini, he perceived a cluster of stars at the 

 foot of Castor, and one in particular, which sensibly increased in diameter while the 

 rest of the stars remained unaltered. Two nights afterwards its place was changed, 

 which originated the idea of its being a cometary body ; an opinion embraced upon the 

 continent when attention was called to it, but soon dispelled by clear evidence of its plane- 

 tary nature. The new planet was named after the reigning monarch by the discoverer, 

 but received his own name from astronomers, which was finally exchanged for the Uranus 

 of heathen mythology, the oldest of the gods, the fabled father of Satur^i and the grandsire 

 of Jupiter referring to the position of the planet beyond the orbits of the bodies named 

 after the latter. By this discovery the extent of the system was at once doubled ; for the 



