are comparatively few, and a person would find some difficulty in collecting two dozen eggs on the morning of that day. birds are very oily, but the young are literally one mass of fat, which has a tallowy appearance, and hence I presume the name of Mutton-Bird. To this I may add that the young birds are very good when fresh, and the old birds after being skinned and preserved in lime are excellent eating. "It is not in my power to describe the scene that presents itself at Green Island on the night of the 24th of November. A few minutes before sunset, flocks are seen making for the island from every quarter, and that with a rapidity hardly conceivable; when they con- The few extracts we have quoted from gregate together, so dense is the cloud, that Mr. Gould's book will give our readers night is ushered in full ten minutes before the some notion of what they may expect from usual time. The birds continue flitting about its perusal; and, beyond this, it would not the island for nearly an hour and then settle upon it. The whole island is burrowed; when I state that there are not sufficient bur- tion of a work emanating from a naturalist rows for one-fourth of the birds to lay in, the so experienced, so skilful, and so faithful as scene of noise and confusion that ensues may Mr. Gould. and be imagined-I will not attempt to describe it. On the morning of the 25th the male birds become us to offer any further recommenda From the Reader. ON THE INVISIBLE RAYS OF THE WE are so accustomed to associate the word ray with the idea of light, that the term dark, or invisible, or obscure rays, stimulates the imagination by its strangeAnd such is more particularly the ness. purpose of collecting the eggs, and again in March or April for curing the young birds. Besides Green Island, the principal rook-case when we are told that the major poreries of these birds are situated between Flin- tion of the radiation of the sun itself is of der's Island and Cape Barren, and most of this invisible character. This great disthe smaller islands in Furneaux's group. The covery was announced sixty-five years ago eggs and cured birds form a great portion of by Sir William Herschel. Permitting a the food of sealers, and, together with the sunbeam to pass through a glass prism, he feathers, constitute the principal articles of formed the coloured spectrum of the solar their traffic. The mode by which the feathers are obtained has been described to me as fol- light; and carrying a small thermometer through its various colours, he determined their heating power. He found this power to augment gradually from the violet to the red; but he also found, to his surprise, that the calorific action did not terminate where the visible spectrum ended. Placing his thermometer in the dark space beyond the red, he found the heating power there to be greater than in any part of the visible lows: "The birds cannot rise from the ground, but must first go into the water; in effecting which, they make numerous tracks to the beach simi lar to those of a kangaroo; these are stopped before morning, with the exception of one leading over a shelving bank, at the bottom of which is dug a pit in the sand; the birds, finding all avenues closed but this, follow each other in such numbers, that, as they fall into the pit, they are immediately smothered by those succeeding them. It takes the feathers of forty birds to weigh a pound; consequently sixteen hundred must be sacrificed to make a feather bed of forty pounds weight. Notwithstanding the enormous annual destruction of these birds, I did not, during the five years that I was in the habit of visiting the Straits, perceive any sensible diminution in their number. The young birds leave the rookeries about the latter end of April, and form one scattered flock in Bass's Straits. I have actually sailed through them from Flinder's Island to the heads of the Tamar, a distance of eighty miles. They shortly afterwards separate into dense flocks, and finally leave the coast. The old FOURTH SERIES. LIVING AGE. VOL. I. spectrum. Sir William Herschel concluded from his experiments that besides those rays which, acting separately upon the retina, produce the sensation of colour, and the sum of which constitutes our ordinary sunshine, a vast outflow of perfectly invisible rays proceeds from the sun; and that, measured by their heating power, the strength or energy of these invisible rays is greater than that of all the visible rays taken together. This result was questioned by some and confirmed by others; but, like every natural truth that can be brought to the test of experiment, the verity of Sir William Her schel's announcement was soon completely the solar spectrum; and representing, as established. Forty years after the dis- Sir William Herschel also had approxicovery of those invisible rays by his fa- mately done, by lines of various lengths the ther, Sir John Herschel made them the thermal intensity at various points, he drew subject of experiment. He made an ar- a curve which expressed the calorific action rangement which enabled him to estimate of the entire spectrum. the heating power of the spectrum by its At various intervals during the last ten drying power. Wetting by a wash of al- years Professor Tyndall has occupied himcohol, paper blackened on one side, he self with the invisible radiation of the eleccasts his spectrum on this paper, and ob- tric light; and to the distribution of heat served the chasing away of the moisture by in its spectrum he directed attention in a the heat of the rays. His drying paper discourse given on the evening of Friday, presented to him a thermograph of the spec- the 20th, at the Royal Institution. The trum, and showed the heating power to ex-instruments made use of were the electric tend far beyond the red. lamp of Duboscq and the linear thermoelectric pile of Melloni. The spectrum was formed by means of lenses and prisms of pure rock-salt. It was equal in width to the length of the row of elements forming through its various colours in succession, and also to search the space right and left of the visible spectrum, the heat falling upon it, at every point of its march, was determined by the deflection of an extremely sensitive galvanometer. By the introduction of the thermo-electric pile Melloni created a new epoch in researches on radiant heat. This instrument enables us to examine, with a precision unattainable with ordinary thermome- the pile, and the latter being caused to pass ters, the distribution of heat in the solar spectrum. Melloni himself devoted some time to this subject. He had made the discovery that various substances, in the highest degree transparent to light, were eminently opaque to those invisible heat-rays. Pure water, for example, is a body of this As in the case of the solar spectrum, the kind. Only one substance did Melloni find heat was found to augment from the violet to be equally pervious to the visible and to the red, while in the dark space beyond the invisible rays, namely transparent rock- the red rose to a maximum. The posisalt. And though the researches of MM. tion of the maximum was about as distant De la Provostaye and Desains, together from the extreme red in the one direction, with some extremely suggestive experi- as the green of the spectrum in the oppoments executed by Mr. Balfour Stewart, show conclusively that Melloni erred in sup- The augmentation of temperature beyond posing rock-salt to be perfectly transparent, the red in the spectrum of the electric light it must be admitted that, in this respect, the is sudden and enormous. Representing the substance approaches very near perfection. thermal intensities by lines of proportional Abandoning prisms of glass, which had lengths, and erecting these lines as perpenbeen always employed previously, Melloni diculars at the places to which they corremade use of a prism of rock-salt in his ex-spond, when we pass beyond the red these periments on the solar spectrum. He was thus enabled to prove that the ultra-red rays discovered by Sir William Herschel formed an invisible spectrum, at least as long as the visible one. He also found the position of maximum radiant power to lie as far on one side the red as the green light of the spectrum on the other. Dr. Franz of Berlin subsequently examined the distribution of heat in the solar spectrum, employing for this purpose a flint-glass prism. He showed that the inaction of the ultra-red rays upon the retina did not arise from the absorption of those rays in the humours of the eye; at all events he proved that a sensible portion of the invisible rays was transmitted across the eye-ball of an ox, and reached the back of the eye. Professor Müller of Freiburg afterwards examined very fully the heat of site one. perpendiculars suddenly and greatly increase in length, reach a maximum, and then fall somewhat more suddenly on the opposite side of the maximum. When the ends of the perpendiculars are united, the curve beyond the red, representing the obscure radiation, rises in a steep and massive peak, which quite dwarfs by its magnitude the radiation of the luminous portion of the spectrum. Interposing suitable substances in the path of the beam, this peak may be in part cut away. Water, in certain thicknesses, does this very effectually. The vapour of water would do the same, and this fact enables us to account for the difference between the distribution of heat in the solar and in the electric spectrum. The comparative height and steepness of the ultra-red peak, in the case of the electric light, are much greater than in the case of the sun, as shown by the diagram of Professor Müller. No doubt the Having thus demonstrated that a power- tercepted in a tube four feet long, by a certain measure of air, oxygen, hydrogen, or nitrogen, transparent ammonia strikes down 7,260 rays, olefiant gas 7,950, while transparent sulphurous acid destroys 8,800. In Professor Tyndall's first experiments on the invisible radiation of the electric light, black glass was the substance made use of. The specimens, however, which he was able to obtain destroyed, along with the visible, a considerable portion of the invisible radiation. But the discovery of the deportment of elementary gases directed his attention to other simple substances. He examined sulphur dissolved in bisulphide of carbon, and found it almost perfectly transOne way of doing this would be to cut off parent to the invisible rays. He also examthe luminous portion of the decomposed beam ined the element bromine, and found that by an opaque screen, allowing the non-lumi- notwithstanding its dark colour, it was eminous portion to pass by its edge. We nently transparent to the ultra-red rays. might then operate at pleasure upon the Layers of this substance, for example, which latter: reflect it, refract it, concentrate entirely cut off all the light of a brilliant gas it. This would be a perfectly philosophical flame, transmitted its invisible radiant heat way of detaching the light from the heat, with freedom. Finally, he tried a solution but with our present means we could not of iodine in bisulphide of carbon, and arthus obtain a quantity of heat sufficient to rived at the extraordinary result that a produce the results intended to be exhibited quantity of dissolved iodine sufficiently before the conclusion of the discourse. opaque to cut off the light of the mid-day Another plan consists in following up a sun was, within the limits of experiment, mode of experiment initiated by Sir Wil- absolutely transparent to invisible radiant liam Herschel. He examined the transmis- heat. sion of solar heat through glasses of various This then is the substance by which the colours, through black muslin and other invisible rays of the electric light may be substances, which intercepted a large por- almost perfectly detached from the visible tion of the solar light. Melloni subsequently ones. Concentrating by a small glass mirdiscovered that lampblack, and also a kind ror, silvered in front, the rays emitted by of black glass, while perfectly opaque to the carbon points of the electric lamp, we light, transmitted a considerable quantity obtain a convergent cone of light. Interof radiant heat. In Professor Tyndall's posing in the path of this concentrated beam "Lectures on Heat," given at the Royal a cell containing the opaque solution of Institution in 1862, and since made public, experiments with these bodies are described. It was while conversing with his friend Mr. Warren De la Rue, in the autumn of 1861, on the possibility of sifting, by absorbents, the light of a beam from its heat, that Professor Tyndall first learned that carbon was the substance which rendered Melloni's glass opaque. This fact was of peculiar interest to him, for it and others seemed to extend to solid bodies a law which he had detected two years previously in his experiments on gases and vapours, and which showed that elementary gases were highly transparent, while compound gases were all more or less opaque -many of them, indeed, almost perfectly opaque -to invisible radiant heat. The enormous differences existing between elementary and compound gases, as regards their opacity to radiant heat, is illustrated by the following facts:- For every ray in iodine, the light of the cone is utterly destroyed, while its invisible rays are scarcely, if at all, meddled with. These converge to a focus, at which, though nothing can be seen even in the darkest room, the following series of effects may be produced: When a piece of black paper is placed in the focus, it is pierced by the invisible rays, as if a white-hot spear had been suddenly driven through it. The paper instantly blazes, without apparent contact with anything hot. A piece of brown paper placed at the focus. soon shows a red-hot, burning surface, extending over a considerable space of the paper, which finally bursts into flame. The wood of a hat-box similarly placed, is rapidly burnt through. A pile of wood and shavings, on which the focus falls, is quickly ignited, and thus a fire may be set burning by the invisible rays. A cigar or a pipe is immediately lighted when placed at the focus of invisible rays His Royal Highness the Comte de Paris performed this experiment at Professor Tyndall's lecture.. Disks of charred paper placed at the focus are raised to brilliant incandescence; charcoal is also ignited there. A piece of charcoal, suspended in a glass receiver full of oxygen, is set on fire at the focus, burning with the splendour exhibited by this substance in an atmosphere of oxygen. The invisible rays, though they have passed through the receiver, still retain sufficient power to render the charcoal within it red-hot. A mixture of oxygen and hydrogen is exploded in the dark focus, through the ignition of its envelope. A strip of blackened zinc-foil placed at the focus is pierced and inflamed by the invisible rays. By gradually drawing the strip through the focus, it may be kept blazing with its characteristic purple light for a considerable time. This experiment is particularly beautiful. Magnesium wire, presented suitably to the focus, burns with almost intolerable brilliancy. The effects thus far described are, in part, due to chemical action. The substances placed at the dark focus are oxidizable ones, which, when heated sufficiently, are attacked by the atmospheric oxygen, ordinary combustion being the result. But the experiments may be freed from this impurity. A thin plate of charcoal, placed in vacuo, is raised to incandescence at the focus of invisible rays. Chemical action is here entirely excluded. A thin plate of silver or copper, with its surface slightly tarnished by the sulphide of the metal, so as to diminish its reflective power, is raised to incandescence either in vacuo or in air. With sufficient battery-power and proper concentration, a plate of platinized platinum is rendered white-hot at the focus of invisible rays; and when the incandescent platinum is looked at through a prism, its light yields a complete and brilliant spectrum. In all these cases we have, in the first place, a perfectly invisible image of the coal points formed by the mirror; and no experiment hitherto made illustrates the identity of light and heat more forcibly than this one. When the plate of metal or of charcoal is placed at the focus, the invisible image raises it to incandescence, and thus prints itself visibly upon the plate. On drawing the coal points apart, or on causing them to approach each other, the thermograph of the points follows their motion. By cutting the plate of carbon along the boundary of the thermograph, we may obtain a second pair of coal points, of the same shape as the original ones, but turned upside down; and thus by the rays of the one pair of coal points, which are incompetent to excite vision, we may cause a second pair to emit all the rays the spectrum. of The ultra-red radiation of the electric light is known to consist of ethereal undulations of greater length, and slower periods of recurrence, than those which excite vision. When, therefore, those long waves inpinge upon a plate of platinum, and raise it to incandescence, their period of vibration is changed. The waves emitted by the platinum are shorter, and of more rapid recurrence, than those falling upon it, the refran gibility being thereby raised, and the invisible rays rendered visible. Thirteen years ago, Professor Stokes published the noble discovery that by the agency of sulphate of quinine, and various other substances, the ultra-violet rays of the spectrum could be rendered visible. These invisible rays of high refrangibility, impinging upon a proper me dium, cause the molecules of that medium to oscillate in slower periods than those of the incident waves. In this case, therefore, the invisible rays are rendered visible by the lowering of their refrangibility; while in the experiments of Professor Tyndall, the ultrared rays are rendered visible by the raising of their refrangibility. To the phenomena brought to light by Professor Stokes, the term fluorescence has been applied by their discoverer, and to the phenomena brought forward on Thursday week at the Royal Society, and on the evening of the following day at the Royal Institution, Professor Tyndall proposes to apply the term calorescence. It was the discovery, more than three years ago, of a substance opaque to light, and almost perfectly transparent to radiant heat- a substance which cut the visible spectrum of the electric light shortly off at the extremity of the red, and left the ultrared radiation almost untouched, that led Professor Tyndall to the foregoing results. They lay directly in the path of his investigation, and it was only the diversion of his attention to subjects of more immediate interest that prevented him from reaching, much earlier, the point which he has now attained. On this, however, Professor Tyndall can found no claim, and the idea of rendering ultra-red rays visible, though arrived at independently, does not by right belong to him. The right to a scientific idea or discovery is secured by the act of Catholic world. Twelve thousand copies publication, and, in virtue of such an act, are sold in Italy alone, though the paper is priority of the conception as regards the as remarkable for the bitterness of its hoscouversion of heat-rays into light-rays, be- tility to Italian freedom as for the fanatic longs indisputably to Dr. Akin. At the Ultramontanism of its doctrine, and the meeting of the British Association, assembled virulence, not to say the ruffianism, of its at New Castle in 1863, he proposed three style. It is of course the organ of the experiments by which he intended to solve special theology, philosophy, and ecclesiasthis question. He afterwards became asso- tical system upheld by the Society, as disciated with an accomplished man of science, tinguished not only from the liberal school Mr. Griffith, of Oxford, and jointly with of Döllinger, but also from the Orthodox him pursued the enquiry. Two out of the Catholic system taught in Louvain. This three experiments proposed at Newcastle by production, which is to strong Catholics Dr. Akin are quite impracticable. In the what the Record is to educated Calvinists, third it was proposed to concentrate by a a paper read but loathed, has just been large burning mirror the rays of the sun, to raised by Pius IX. in a solemn Brief cut off the luminous portion of the radiation addressed to the world to the position of by 'proper absorbents,' and then to operate authorized defender and exponent of the with the obscure rays. Dr. Akin employed Catholic faith. Its writers are formed into in his experiments a mirror thirty-six inches a College in perpetuity, absolutely dependin diameter, but he has hitherto failed to re-ent on the General of the Society of Jesus, alize his idea. With a mirror four inches and formally authorized to compose and in diameter, the radiant source with which his researches had rendered him familiar, and a substance which he had himself discovered to filter the beam of the electric lamp, Professor Tyndall obtained all the results above described. From The Spectator, 21st April. publish writings on behalf of the Holy Faith AN event of great importance has just occurred in Rome, which, like most Roman events, has escaped attention in Great Britain. The Civilta Cattolica, the Jesuit newspaper, has been suddenly raised by an exercise of the Pope's plenary authority to the position of an integral part in the organization of the Catholic Church. This journal was founded by the Society of Jesus in 1850, and was originally published in Naples, but its editors could not entirely conceal their belief in the great dogma of the "Company," the supremacy of the Papacy over all temporal authority; and Ferdinand, though a bigot by nature and an Ultramontane by policy, was still a Bourbon, prepared to worship the Pope as long as the Pope supported the secular authority, and to resist him if he interfered with any royal The Society in fact is at the zenith of its prerogative. He ordered the Society and influence over the Catholic organization, their paper alike to quit Naples. The and is becoming imprudent in the plenitude Civilta Cattolica was consequently removed of its security. Its rulers have just struck to Rome, and the whole influence of the another blow which has profoundly irritated Society exerted to extend its circulation, even the interior hierarchy of Rome. For which speedily became unrivalled in the fifteen years past the Society has been try |