TO 1837.]

RELIGIOUS PROGRESS IN IRELAND.

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though, in consequence of the constant current of emigra- and directing the currents of religious progress in Ireland tion, we have not the same means of measuring it statisti- since the reign of George III. The first of these is the cally as in this country. The agitation in favour of Catholic Rev. B. W. Mathias, minister of the Bethesdan proprietary Emancipation, and the action of the Catholic Association, church in Dublin, in which "the gospel" was first reguhad the effect of rousing the Protestants from their apathy, larly preached, in the evangelical sense of the term. Mr and kindling a sort of polemical war between the parties, Mathias was the first secretary of the Hibernian Bible which was provoked by Dr. Doyle, O'Connell, and a Society. As a preacher he was eloquent, with a style disnumber of the lay agitators. Contemporaneous with this tinguished by simplicity and pathos. The Rev. Peter was the diffusion of a missionary spirit among Church Roe, of Kilkenny, was another of the pioneers of evanpeople, owing to the exertions of the Irish Evangelical gelism, who exerted great influence in his day. As a Society, the London Hibernian Society, and other English speaker he was weighty, instructive, and impressive. The

agencies. At the same time Dr. Singer, one of the Fellows of Trinity College, and professor of divinity, the Rev. Mr. Cæsar Otway, and a few other ministers, began to gather around them a number of young clergymen and divinity students, who formed the nucleus of the evangelical party, which has since spread so as to become almost commensurate with the Irish Church. The following is a very brief sketch of the leading men who either by labour in the pulpit, or on the platform, or in the committees of religious societies, or by their property and influence-were mainly instrumental in awakening the spirit of revival,

VOL. VII.-No. 343.

Rev. R. Daly, afterwards Bishop of Cashel, influential from his position as rector of Powerscourt, was energetic, active, and a olever controversialist. The most effective of this small band was Dr. Singer, afterwards the bishop of Meath, who brought learning, taste, and eloquence to the defence of the gospel and the promotion of the evangelical cause. The Rev. J. Carlile, D.D., one of the ministers of the Scotch Church, laboured indefatigably, as secretary to the Bible Society and otherwise, in furtherance of Protestant views, and contributed more to its success by his clear head and business habits than others by their

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SCIENTIFIC DISCOVERIES.

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combination of national efforts in collecting reliable data from the remotest corners of the globe, is characteristic of the practical energy of the age. Chemistry has been cultivated with extraordinary assiduity; but none of the many discoveries in that science is comparable in importance to that which was made by Dalton. To cite, then, at present but a few names, amongst the most conspicuous benefactors of science of the last or contemporary period are-Airy, Cauchey, Hamilton, and M'Cullagh; Faraday, Melloni, and Gauss; Sir John Herschel, M. Struve, and Lord Rosse; Plana, Poisson, Leverrier, and Adams; Mitscherlich, Liebig, and Dumas.

says Professor James Forbes, "we compare the now ex-philosopher of Germany it has found its Kepler; and the tensive subjects of heat, electricity, and magnetism, with the mere rudiments of these sciences as understood in 1750, or if we think of the astonishing revival of physical and experimental optics (which had well nigh slumbered for more than a century, during the too short lives of Young and Fresnel), we shall be disposed to admit the former part of the statement; and when we recollect that the same period has given birth to the steam-engine of Watt, with its application to shipping and railways; to the gigantic telescopes of Herschel and Lord Rosse, wonderful as works of art as well as instruments of sublime discovery; to the electric telegraph, and to the tubular bridge, we shall be ready to grant the last part of the proposition, that science and art have been more indissolubly united than at any previous period." Of the great discoverers of the former period, several survived and continued their efficient labours during no small portion of the latter, claiming, as they were were well entitled to do, the respect and veneration of their disciples and successors; but the vast steps so recently made in optics, in electricity, in magnetism, in the theory of heat, and in chemical principles, tended of necessity to call forth such an amount of laborious detail in the defining and connecting of facts and laws, and the deductions of the theories started to explain them, as seemed to render fresh and striking originality somewhat hopeless; whilst they occasioned a vast amount of useful employment to minds of every order of talent. The undulatory theory of light, developed by the massive labours of Young and Fresnel, has afforded still unexhausted material to the mathematician on the one hand, and to the experimentalist on the other; and ably have they fulfilled the double task, adding at the same time discoveries, whose importance and difficulty would have made them still more prominent had they not been the legitimate consequences of a still greater discovery already in our possession. Nearly the same might have been said for the sciences of electricity, electro-magnetism, electro-chemistry, had not the comparative newness of the whole doctrine of these sciences, the suddenness of their first rise, and perhaps still more the appearance of a philosopher of the very highest merit-Faraday, who fortunately attached himself to this special department-made the last thirty years an almost unbroken period of discovery. Radiant heat, too, has been successfully advanced by labours, comparable perhaps to those which marked its first rise as a science: and some other topics connected with heat have risen into great and practical consequence. Astronomy has been prosecuted with a systematic assiduity and a success, especially at the British and Russian national observatories, which have been exceeded at no former period; whilst physical astronomy has been cultivated by methods of still improved analysis, and has achieved what is admitted to be one of the most brilliant discoveries of the present century. This was the prediction, simultaneously by an English and a French astronomer, of the position in space of the planet Neptune, whose existence was unknown except by the disturbance which it produced in the movements of the planet Uranus. Terrestrial magnetism has for the first time aspired to the rank of an exact science. In an illustrious

Until the commencement of the present century, the state of mathematical science was very low in England, and was regarded on the Continent with the greatest contempt. The commencement of a better era originated with Woodhouse at Cambridge and Playfair in Edinburgh, by both of whom the Continental methods were introduced into the studies of their respective universities; whilst Ivory, a native of Scotland, earned for himself, by his writings, a place in the list of great living mathematicians. About 1820 the translation of La Croix's "Differential Calculus," superintended by Sir John Herschel and Dean Peacock, came into use as a university text-book. Soon after, the writings of La Place and Poisson, as well as other Continental mathematicians, were generally read in our universities; and a few men of active and daring minds, chiefly of the Cambridge school, such as Prof. Airy and Sir John Lubbock, grappled with the outstanding difficulties of physical astronomy; whilst a larger number applied themselves to the most difficult parts of pure analysis, and acquired great dexterity in its use, in the solution of geometrical and mechanical problems. Such, for example, were Mr. Babbage, Mr. A. De Morgan, Mr. Murphy, and Mr. Green; and in the first rank of such mathematicians stood Sir William R. Hamilton and J. M'Cullagh of Dublin. No new calculus, or great general method in analysis, has resulted from these persevering labours, whether from British or foreign mathematicians; but an increased facility and power in applying the existing resources of mathematics to the solution of large classes of problems previously intractable, or resolved only indirectly, or by approximation, have been obtained. Every year and every civilised community contributed to these real improvements. An almost new branch of abstract science (faintly shadowed by Leibnitz) came into existence at this time-the separation of symbols of operation from symbols of quantity, and the universal employment of the former. Sir John Herschel and Olinthus G. Gregory were among the most active introducers of this improvement in algebra; but few of the more eminent living British or foreign mathematicians have failed to contribute their share to the metaphysical department of analysis. Sir John F. W. Herschel, son of Sir William Herschel, conversant with almost every branch of science devoted himself with remarkable success to the cultivation of sidereal astronor y, bearing a name honoured and revered by all. Science owes much to Sir William Herschel and his son. Sir William was one of those who

appeared at one time to have brought the invention to its highest perfection, but the earl of Rosse has made an important step further, not only by constructing a larger telescope, but by adapting machinery driven by steampower to the grinding and polishing of the mirrors; so that the largest speculum may be finished with nearly the same accuracy and expedition as the smallest. The chef

may be said to have created physical astronomy. He was born at Hanover in 1738. His father being a musician, with limited means and a large family, he was under the necessity of devoting the first portion of his life to the musical profession; but this did not prevent him from indulging his predilections for the study of philosophy. Desiring more favourable opportunities for advancing in the path of knowledge, and hoping to find them in Eng-d'œuvre of Lord Rosse is a telescope of six feet aperture, land, he left Hanover in 1757; but when he arrived in this country he had to struggle with great difficulties at first, and was dependent on his skill in music for a means of support. Having obtained a situation, however, as organist, he was enabled to purchase a few mathematical works; and he soon devoted himself to astronomy with all the ardour of a passion. He was not able to procure a telescope, on account of his limited means; but he determined to construct one, and succeeded. With it he saw Saturn's ring and the satellites of Jupiter; and, seven years after, Uranus, a planet situated beyond what had been, up to that time, considered as the limits of the universe. This turned the eyes of all Europe towards him. George III. bestowed on him a pension and a residence, where, in his observatory, he continued his astronomical researches with great success. He was now loaded with honours, and the most celebrated scientific bodies eagerly enrolled him among their members; and he persevered in his valuable researches until his death, in 1822. He was succeeded in his labours by his son, John Frederick William; who was worthy to inherit a name on which he reflected additional lustre. England could claim the father only by adoption: she calls the son hers by birth. The latter evinced very early a taste for mathematics, but did not devote himself to astronomy until after his father's death. He then gave himself up to it without reserve; and the value of his laborious observations was recognised, not only here, but on the Continent. At that period the Southern Hemisphere was to astronomers little more than an unknown region. For the purpose of exploring it, he visited the Cape of Good Hope, where, making use of his father's method, he continued his observations for more than four years, examining with great care, among other things, the nebulæ and double stars. On his return to Europe, he gave the results of his labours to the world in a work of great interest, and of the highest importance; and the value of the services he had rendered to science was recognised, not only by the scientific world, but by his sovereign also, who created him a baronet, and he was appointed Master of the Mint. After this period he took no further part in practical astronomy, but he published many excellent works, not only on that subject, but on science generally; and he displayed a thorough acquaintance with natural history, the belles lettres, and the fine arts, and translated a portion of the "Iliad." This great astronomer and mathematician died in May, 1871.

It is a remarkable circumstance that as the reflecting telescope was of British invention, so the more important improvements and applications of it have been almost confined to the United Kingdom. It is also worthy of notice that its manufacture has prospered more in the hands of amateurs than of regular opticians. Sir William Herschel

and 53 or 54 feet of focal length. It was completed in the latter end of 1844, and erected in his demesne at Parsonstown, King's County, Ireland. It is the largest telescope ever constructed. The machinery is supported on massive walls, and, notwithstanding its great weight and size, it is moved with the utmost ease, and can be lowered to any angle, while it sweeps the horizon, by means of wheels running on a graduated circle. Its cost exceeded £30,000. Lord Rosse's success was the triumph of persevering exertion and mechanical skill. His assistants were his own countrymen, instructed by himself in his own workshops, where the very steam-engine which drives the polisher was fabricated. His labours to improve the telescope commenced about 1828, and continued unremittingly until 1844. "Commencing with a variety of ingenious attempts to correct spherical aberration, and to overcome the extreme difficulty of procuring and manufacturing large castings of so excessively brittle a material as speculum metal, they terminated in the rejection of all minor helps and expedients, and in the fortunate completion, at a single casting, of immense mirrors, which were of a correctly parabolic figure when ground and polished. The speculum of his large telescope, weighing four tons, and having a surface considerably more than twice as large as that of Sir William Herschel's forty-feet instrument, was polished in six hours. Many difficulties in detail were met in the mounting and use of so gigantic à mass, particularly on account of the distortion of the mirror by flexure; but these were gradually overcome, and he was amply rewarded for his efforts by the success of his observations. Many nebula which resisted the power of former telescopes were 'resolved' into stars by the six-feet speculum. The aspect of a great number of nebulæ described by the two Herschels is materially modified, by the power of Lord Rosse's telescope to embrace the fainter prolongations of these singular objects. In general, the regularity of form is very much lessened, and in many cases vanishes altogether. Instead of these, a certain species of symmetry, of a vague yet remarkable description, has been detected. It is a spiral arrangement of the nebulous coils round a centre, resembling somewhat the emanations of revolving fireworks."

M. Arago, who was forty years in charge of the observatory of Paris, was a great astronomer, but he did not, indeed, avail himself of that position to enlarge the domain of his science as much as he might have done; he made, however, some important optical discoveries, and was very instrumental in calling forth the genius of Fresnel, and obtaining a public recognition of the labours of Young. "The undulatory theory of light" stands where it does in no slight degree through the instrumentality of Arago. In 1838 he indicated the application of Mr. (afterwards

Sir) C. Wheatstone's invention of the revolving mirror, as a means of measuring intervals of time incredibly short, in order to compare the velocity of light in air, and in a corresponding length of water. Arago was regarded as having proved the long-suspected connection between the aurora borealis and the freely suspended magnet.

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'Systems of Rays.' To Dr. Lloyd we are indebted for several interesting experimental papers on optics, for an impartial review of the progress of the science, and for an excellent elementary treatise on the wave theory, which forms by far the most popular introduction to the subject."

Closely associated in his pursuits as in personal friendship with Sir W. Hamilton and Dr. Lloyd was James M'Cullagh, a native of the County Tyrone, who died prematurely by his own hand in 1847, under the pressure of a fit of despondency brought on by excessive application to study, accompanied by neglect and imprudence in regard to his diet and to the laws of health. His unhappy end was greatly lamented, for he was equally beloved for his amiable and exemplary character, and admired for his genius. In the galaxy of illustrious names that shed light upon this age, not the least conspicuous is that of Mary Somerville, who is known in British science, not only as the able commentator of "La Place's Mécanique Céleste," but as the author of some ingenious experiments on the magnetising power of the violet ray, and on the permeability of different bodies to the chemical rays, similar to those of Melloni on the heating rays; and she found great and seemingly capricious variations in this respect. The beautiful invention of the stereoscope, one of the most interesting contri

Amongst the foremost of the promoters of science, and the most eloquent of its expounders, was Sir David Brewster, who died full of years and of honours in 1868. Arrived at manhood at the opening of the present century, having been born in 1781, he continued his brilliant course during fifty years, pursuing his investigations into the laws of polarisation by crystals, and by the reflection, refraction, and absorption of light, in which he made important discoveries. "His papers," says Professor Forbes, are so numerous, and their variety so great, as to render an enumeration, even of those containing what may reasonably be termed discoveries, impossible within our limits. Few persons have made with their own eyes so vast a number of independent observations; few have ever observed better or recorded their observations more faithfully. His scientific glory is different in kind from that of Young and Fresnel; but the discoverer of the law of polarisation, of biaxal crystals, of optical mineralogy, and of double refraction produced by compression, will always occupy a foremost rank in the intel-butions made to the theory of vision, was the work of Mr. lectual history of the age."

The attention of the British public was forcibly arrested by an able treatise on "Light," contributed by Sir John Herschel, in 1827, to the "Encyclopædia Metropolitana." Its excellent method and lucid explanations attracted to the theory of Young and Fresnel men of science who had been deterred by the fragmentary and abstruse style of the former. This was followed four years later by a most able and precise mathematical exposition of the theory, and its application to optical problems, by Prof. Airy, who afterwards became astronomer royal. The writings of Prof. Airy and of Sir John Herschel have continued to be valuable sources of information on this subject, and on physical optics generally, not only in this country, but on the Continent.

While an impulse was thus given to the mathematical theory of light in the University of Cambridge, a similar progress was being made in the sister University of Dublin, where three of her most eminent professors-Sir William Rowan Hamilton, Dr. Lloyd, and Mr. M'Cullagh-devoted themselves energetically to its improvement and verification. Sir William Hamilton, a geometer of the first order, having undertaken a more complete discussion of the wave surface of Fresnel, to the equation of which he gave a more elegant form, ascertained the exact nature of that surface, and consequently the exact direction of refracted rays in the neighbourhood of the optic axes. The beautiful and unexpected results he obtained were verified by his friend Dr. Lloyd. The names of Sir W. Hamilton and Dr. Lloyd will be handed down to posterity in connection with this discovery. "But," says Professor Forbes, "they have other claims to our respect. The former has generalised the most complicated cases of common geometrical optics, by a peculiar analysis developed in his essays on

Wheatstone, who published an account of it in the "Philosophical Transactions" of 1838.

In connection with experiments of this class should be mentioned the invention of the daguerreotype, or the production of permanent pictures on plated copper, in 1825, which was brought to perfection in 1839 by Daguerre, whose name it bears. About the same time Hervey Fox Talbot applied himself to similar experiments, and invented the calotype, or the production of permanent pictures on paper; and by a subsequent invention he obtained what he justly called "an instantaneous process." An image was formed in a camera-a revolving wheel, to which was affixed a printed bill. The room being darkened, and the wheel made to revolve with the speed of 200 revolutions in a second, and being then illuminated by an electric spark, a legible impression of the printing was obtained. We doubt if in the whole history of physics a more astonishing result is recorded. Thus H. Fox Talbot, by his rare energy, brought his inventions almost to perfection. Numerous competitors of course appeared on the field, and obtained many interesting results. The talbotype was undoubtedly a great improvement on the daguerreotype process, which, besides requiring extraordinary care in the preparation of the plate, and in the process itself, demanded a costly material; but its great defect was the difficulty, if not impossibility, of rendering a paper surface suitable to the requirements of photography. Hence the use of a film of albumen on glass, by M. Niepce de St. Victor, in 1848, was a step considerably in advance; and still further progress was made by the use of collodion in the same way by M. le Gray, in 1850. By the employment of collodion, the process, from being one of extreme difficulty and uncertainty, became one that could be performed with great ease and certainty. An