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tion for a moment. He would not even take his hand from what he was about to help himself to food; and the little that he ate on such occasions was put into his mouth by his sister. He gave the mirror its proper shape more by a certain natural tact than by rule; and when his hand was once in, as the phrase is, he was afraid the perfection of the finish might be impaired by the least intermission of his labours.

It was on the 13th of March, 1781, that Herschel made the discovery to which he owes, perhaps, most of his popular reputation. He had been engaged for nearly a year and a half in making a regular survey of the heavens, when, on the evening of the day that has been mentioned, having turned his telescope (an excellent seven-feet reflector, of his own constructing) to a particular part of the sky, he observed among the other stars one which seemed to shine with a more steady radiance than those around it; and, on account of that and some other peculiarities in its appearance, which excited his suspicions, he determined to observe it more narrowly. On reverting to it after some hours he was a good deal surprised to find that it had perceptibly changed its placea fact which, the next day, became still more indisputable. At first he was somewhat in doubt whether or not it was the same star which he had seen on these different occasions; but, after continuing his observations for a few days longer, all uncertainty upon that head vanished. He now communicated what he had observed to the Astronomer Royal, Dr. Maskelyne, who concluded that the luminary could be nothing else than a new comet. Continued observation of it, however, for a few months, dissipated this error; and it became evident that it was, in reality, a hitherto undiscovered planet. This new world, so unexpectedly found to form a part of the system to which our own belongs, received from Herschel the name of the Georgium Sidus, or Georgian Star, in honour of the King of England; but by continental astronomers it has been more generally called either Herschel, after its discoverer, or Uranus. Subsequent observations, made chiefly by Herschel himself, have ascertained many particulars regarding it, some of which are well calculated to fill us with astonishment at the powers of the sublime science which can wing its way so far into the immensity of space, and bring us back information so precise and various. The diameter of this new globe has been found to be nearly four and a half times larger than that of our own. Its size altogether is about eighty times that of our earth. Its year is as long as eighty-three of ours. Its distance from the sun is nearly eighteen hundred millions of miles, or more than nineteen times that of the earth. Its density, as compared with that of the earth, is nearly as twenty-two to one hundred; so that its entire weight is not far from eighteen times that of our planet. Finally, the force of gravitation near its surface is such, that falling bodies descend only through fourteen feet during the first second, instead

of thirty-two feet, as with us. Herschel afterwards discovered, successively, no fewer than six satellites, or moons, belonging to his new planet. The announcement of the discovery of the Georgium Sidus at once made Herschel's name universally known. In the course of a few months the king bestowed upon him a pension of three hundred a year, that he might be enabled entirely to relinquish his engagements at Bath; and upon this he came to reside at Slough, near Windsor. He now devoted himself entirely to science; and the constructing of telescopes, and the observation of the heavens, continued to form the occupations of the remainder of his life. Astronomy is indebted to him for many other most interesting discoveries beside the celebrated one which we have just noticed, as well as for a variety of speculations of the most ingenious, original, and profound character. But of these we cannot here attempt any detail. He also introduced some important improvements into the construction of the reflecting telescope-besides continuing to fabricate that instrument of dimensions greatly exceeding any that had been formerly attempted, and with powers surpassing, in nearly a corresponding degree, what had ever before been obtained. The largest telescope which he ever made was his famous one of forty feet long, which he erected at Slough, for the king. It was begun about the end of the year 1785, and on the 28th of August, 1789, the enormous tube was poised on the complicated but ingeniously contrived mechanism by which its movements were to be regulated, and ready for use. On the same day a new satellite of Saturn was detected by it, being the sixth which had been observed attendant upon that planet. A seventh was afterwards discovered by means of the same instrument. This telescope has since been taken down, and replaced by another of only half the length, constructed by Sir John Herschel, the distinguished son of the subject of our present sketch. Herschel himself eventually became convinced that no telescope could surpass in magnifying power one of from twenty to twenty-five feet in length. The French astronomer, Lalande, in his continuation of Montucla's "Histoire des Mathématiques," states, that he was informed by George III. himself, that it was at his desire that Herschel was induced to make the telescope at Slough of the extraordinary length he did, his own wish being that it should not be more than thirty feet long.

So extraordinary was the ardour of this great astronomer in the study of his favourite science, that for many years, it has been asserted, he never was in bed at any hour during which the stars were visible. And he made almost all his observations, whatever was the season of the year, not under cover, but in his garden, and in the open air, and generally without an attendant. There was much that was altogether peculiar to himself, not only in the process by which he fabricated his telescopes, but also in his manner of using them. One of the attendants in the

king's observatory at Richmond, who had formerly been a workman in Ramsden's establishment, was forcibly reminded, on seeing Herschel take an observation, of a remark which his old master had made. Having just completed one of his best telescopes, Ramsden, addressing himself to his workmen, said, "This, I believe, is the highest degree of perfection that we opticians by profession will ever arrive at; if any improvement of importance shall ever after this be introduced in the making of telescopes, it will be by some one who has not been taught his art by us."

Some years before his death the degree of Doctor of Civil Law was conferred upon Herschel by the University of Oxford; and in 1816 George IV., then Prince Regent, bestowed upon him the Hanoverian and Guelphic Order of Knighthood. He died on the 23rd of August, 1822, when he was within a few months of having completed his eightyfourth year.

To this distinguished name, and those of Dollond and Ramsden, it would be easy, if our space permitted, to add those of many other selftaught cultivators of the same departments of science. Among more recent opticians, no one has attained a higher eminence, either as an artist or as a scientific experimentalist and speculator, than FRAUNHOFER, late superintendent of the establishment for the manufacture of optical glasses at Munich, who rose from the condition of a common workman. Of astronomical observers, again, some might also be mentioned who have been of very humble station. There is a print—a copy of which may be seen in the rooms of the Astronomical Society-of two very remarkable individuals who were employed during a considerable part of the last century in the Earl of Macclesfield's observatory at Sherburn. The elder of these, as the inscription below the engraving informs us, was named THOMAS PHELPS, and he, it is stated, "from being a stableboy, in the year 1718, to the then Lord Chief Justice Parker, afterwards Earl of Macclesfield, rose by his merit to the upper employments in the family, and at last, for his uncommon genius, was promoted to be Observer in the observatory at Sherburn Castle." Phelps, it is added, was born at Chalgrove, in Oxfordshire, in January, 1694, and was in his eighty-second year when his portrait was taken. The other, JOHN BARTLETT, is described as having been "originally a shepherd, in which station he, by books and observation, acquired such a knowledge in computation, and of the heavenly bodies, as induced the late George, Earl of Macclesfield, to appoint him Assistant Observer in his observatory at Sherburn Castle." Bartlett was born at Stoke Talmage, in Oxfordshire, August 22, 1721, o. s., and was in his fifty-fourth year at the time his picture was taken. In the print Phelps is represented as standing looking through a telescope, while Bartlett is sitting by him with his tablets, or a sheet of paper, in the one hand, and a pen in the other, ready, seemingly, to note down what his associate may announce.

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Phelps-Bartlett-Palitzch.

479 There is a penetrating eagerness and sagacity in the eye and general aspect of the old man; and that of the other is also a striking head, with a less keen and vivacious physiognomy than Phelps, but more massive, and indicating, perhaps, more of a meditator and calculating mind. In a manuscript note on the back of the copy of this print, which belongs to the Astronomical Society, it is stated that "Phelps was the person who, on the 23rd of December, 1743, discovered the great comet, and made the first observation of it; an account of which is contained in the 'Philosophical Transactions,' but not the name of the observer." The comet of 1758, so famous in consequence of its return having been predicted more than half a century before by the great astronomer Halley, was also, it may be remarked, first perceived by an observer in an humble rank of life. It was on the 25th of December in that year that the luminary in question was detected with only the naked eye, at Prohlis, near Dresden, by a Saxon peasant of the name of PALITZCH, at a time when all the greatest astronomers in Europe were seeking for it in vain with their telescopes. Nor did Palitzch owe his discovery merely to his superior powers of vision. This Saxon peasant was really an astronomer. 'George Palitzch," says Lalande, "born in the obscure condition of a common labourer, had succeeded both in finding happiness in his humble lot, and in acquiring various branches of knowledge which are rarely found possessed by men of higher stations who have had the advantage of a careful education. More in the way of being struck with the spectacle of the heavens than if he had lived in a town, he had, by his own efforts, studied and made himself master of astronomy, as well as those parts of geometry, such as plain and spherical trigonometry, upon which it depends. By the exertion of a meritorious economy he had formed for himself an observatory, furnished with the instruments most important for the pursuit of his favourite study. Few opportunities of making interesting observations escaped him; and notwithstanding this his occupations as an agriculturist were duly attended to. Natural History and Botany were also among the studies in which he took great delight; and he had a very well arranged cabinet of natural productions, as well as a garden full of rare plants, which he carefully cultivated. He was distinguished by such exceeding modesty, that he always refused even to give any details of his life, notwithstanding they must have been so full of interest. Such was the astronomer and philosopher Palitzch, to whom was reserved the honour of being the first of all the astronomers of Europe in the discovery of the return of this anxiously expected comet." Palitzch, we may add, who was born in 1723, continued to cultivate astronomy, as well as his garden and his fields, for many years after this event, and died at last in his native village in 1788. He had been for some time a corresponding member both of the Royal Society of London and of the Imperial Academy of St. Petersburg.

CHAPTER XXXVII.

DISCOVERY AND IMPROVEMENT OF THE STEAM-ENGINE:

JAMES WATT.

ALL the inventions and improvements of recent times, if measured by their effects upon the condition of society, sink into insignificance when compared with the extraordinary results which have followed the employment of steam as a mechanical agent; and the merit and honour of having first rendered it extensively available for that purpose are pre-eminently due to one individual, the illustrious JAMES WATT. The force of steam, now so important an agent in mechanics, was nearly altogether overlooked until within the last two centuries. The only application of it which appears to have been made by the ancients was in the construction of the instrument which they called the Eolipile, that is, the Ball of Æolus. The Æolipile consisted of a hollow globe of metal, with a long neck, terminating in a very small orifice, which, being filled with water and placed on a fire, exhibited the steam, as it was generated by the heat, rushing with apparently great force through the narrow opening. A common teakettle, in fact, is a sort of Æolipile. The only use which it was proposed to make of this contrivance was to apply the current of steam, as it issued from the spout, by way of a moving force-to propel, for instance, the vans of a mill, or, by acting immediately upon the air, to generate a movement opposite to its own direction. But it was impossible that any useful purpose should have been effected by such methods of employing steam. Steam depends so entirely for its existence in the state of vapour upon the presence of a large quantity of heat, that it is reduced to a mist or a fluid almost immediately on coming into contact either with the atmosphere, or anything else which is colder than itself; and in this condition its expansive force is gone. The only way of employing steam with much effect, therefore, is to make it act in a close vessel. The first known writer who alludes to the prodigious energy which it exerts when thus confined is the French engineer Solomon de Caus, who flourished in the beginning of the seventeenth century. This ingenious person, who came to England in 1612 in the train of the Elector Palatine, afterwards the son-in-law of James I., and resided here for some years, published a folio volume at Paris in 1623 on moving forces; in which he states, that, if water be sufficiently heated in a close ball of copper, the air or steam arising from it will at last burst the ball, with a noise like the going-off of a petard. In another place, he actually describes a method of raising water, as he expresses it, by the aid of

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