Luminous Bodies Research Articles

On the Great Sun-spot of June 1843*

ONE of the largest and most remarkable spots ever seen on the sun's disc appeared in June 1843, and continued visible to the naked eye for seven or eight days. The diameter of this spot was, according to Schwabe, 74,000 miles; so that its area was many times greater than that of the earth's surface. Now, it has been observed during a number of sun-spot cycles that the larger spots are generally found at or near the epoch of the greatest numbers. The year 1843 was, however, a minimum epoch of the eleven-year cycle. It would seem, therefore, that the formation of this extraordinary spot was an anomaly, and that its origin ought not to be looked for in the general cause of the spots of Schwabe's cycle. As having a possible bearing on the question under consideration, let us refer to a phenomenon observed at the same moment, on the 1st September, 1859, by Mr. Carrington, at Redhill, and Mr. Hodgson, at Highgate. “Mr. Carrington had directed his telescope to the sun, and was engaged in observing his spots, when suddenly two intensely luminous bodies burst into view on its surface. They moved side by side through a space of about thirty-five thousand miles, first increasing in brightness, then fading away. In five minutes they had vanished. … It is a remarkable circumstance that the observations at Kew show that on the very day, and at the very hour and minute of this unexpected and curious phenomenon, a moderate but marked magnetic disturbance took place, and a storm, or great disturbance of the magnetic element, occurred four hours after midnight, extending to the southern hemisphere. “The opinion has been expressed by more than one astronomer that this phenomenon was produced by the fall of meteoric matter upon the sun's surface. Now the fact may be worthy of note that the comet of 1843, which had the least perihelion distance of any on record, actually grazed the solar atmosphere about three months before the appearance of the great sun-spot of the same year. The comet's least distance from the sun was about 65,000 miles. Had it approached but little nearer, the resistance of the atmosphere would probably have brought its entire mass to the solar surface. Even at its actual distance it must have produced considerable atmospheric disturbance. But the recent discovery that a number of comets are associated with meteoric matter, travelling in nearly the same orbits, suggests the inquiry whether an enormous meteorite following in the comet's train and having a somewhat less perihelion distance, may not have been precipitated upon the sun, thus producing the great disturbance observed so shortly after the comet's perihelion passage.

Letter from the Rev. Mr. Read respecting the Luminous Bodies seen on Sept. 4, 1850. (See Monthly Notices, vol. xi. p. 48.)

Letter from the Rev. Mr. Read respecting the Luminous Bodies seen on Sept. 4, 1850. (See Monthly Notices, vol. xi. p. 48.)

Observations upon the radiation of luminous bodies

Observations upon the radiation of luminous bodies

On the adaptation of different modes of illuminating Light-houses, as depending on their situations and the object contemplated in their erection. By William Henry Barlow, Esq., in a letter addressed to Peter Barlow, Esq., F. R. S., and communicated by him

The letter of Mr. W. H. Barlow, addressed to his father, in which the paper is contained, is dated Constantinople, March 14th, 1837, and states that the experiments which he made with the Drummond light, and other means of illuminating Light-houses, and of which he now communicates the results, were undertaken at the request of the Turkish Government, with the view of placing lights at the entrance of the Bosphorus from the Black Sea. The object of his inquiry is to investigate the principles on which the illuminating power, resulting from the employment of reflectors, and of lenses, depends; and the most advantageous application of that power to the purposes of Light-houses. In discussing the relation which exists between the illuminating power and the intensity of an artificial light, he observes that the former is proportional to the quantity of light projected on a given surface at a given distance; and that the latter is dependent on the quantity of light projected by a given area of the luminous body on a given surface at a given distance. Hence the intensity of a light multiplied into its surface is the measure of the illuminating power, whether the light proceed from one or from several luminous bodies: and the illuminating power is equal to that of a sphere of light, whose intensity and apparent surface are equal to that of the light itself at any given mean distance.

Quelques remarques sur la chaleur, et sur l' action des corps qui l'interceptent

The remarks here brought forward relate chiefly to Dr. Herschel’s experiments on the solar and terrestrial rays that occasion heat, pub­lished in the Philosophical Transactions for the year 1800, and are meant to rectify some anomalies which appear in their results. The paper consists of two parts: the first being the observations on Dr. Herschel’s experiments, and some new ones, with inferences deduced from them; and the second the exposition of a theory, which the author thinks may reconcile all contradictions. In the first part he sets out with briefly stating the manner in which Dr. Herschel conducted the experiments he made, in order to estimate, by the indications of different thermometers, the quantity of heat transmitted through various substances, compared with the heat afforded by direct rays from different luminous bodies, or more properly sources of heat. Here the author soon starts a difficulty concerning the mode of estimating the intercepting power of the substances used in the experiments. As these experiments consist of a series of observations made progressively at intervals of one mi­nute between each other, it follows that the ratio Dr. Herschel adopted between the heat produced by direct rays, and those transmitted through coloured media, is not, as he imagined, a constant proportion, he having uniformly deduced his inferences from the differences be­tween the initial and the final degrees of heat; whereas, had he at­tended to the intermediate observations, he would have found that each of them would have afforded a different ratio.

Experiments on the solar, and on the terrestrial rays that occasion heat; with a comparative view of the laws to which light and heat, or rather the rays which occasion them, are subject, in order to determine whether they are the same, or different

In the prefatory part of this paper, the author found it necessary to limit the sense he affixes to the word heat ; and after excluding the late terminology of latent , absolute , specific , sensible heat, the matter of heat , caloric , and even radiant heat , which last, however, comes nearest to the expression he has adopted, he desires to be understood, that, in speaking of rays which occasion heat , he does not mean that those rays themselves are heat, but that he here considers heat merely as the effect of a cause, the nature of which is no part of his present inquiry. Having thus determined the subject of his investigation, the Doctor distinguishes heat into six different kinds; whereof three are solar, and three terrestrial. These, however, are reducible into three general divisions, each of the solar and terrestrial kinds resembling each other respectively. The first is the heat produced by luminous bodies, whether by the sun or by terrestrial flames. The second comprehends the heat of coloured radiants, such as that of the sun separated by a prism, and that of culinary fires openly exposed. And the third relates to heat from radiants, where neither light nor colour can be perceived; such as the heat of invisible solar rays, refracted by a prism, which have been the subject of a former paper; and the terrestrial heat from fires inclosed in stoves, and from metals heated short of the lowest degree of incandescence.

A continuation of the experiments and observations on the light which is spontaneously emitted from various bodies; with some experiments and observations on solar light, when imbibed by Canton’s phosphorus

A short description is here premised of an apparatus for exposing luminous bodies to different kinds of air, which, in addition to the well-known glass phial or tube inverted in water, consists in a small stand, to the top of which the luminous substance is fixed, and thus inserted into the inverted phial, into which the species of air to be employed is previously let up to the quantity of about eight ounces. With these instruments a copious set of experiments has been made, of which the following are the principal results. In common or atmospherical air, all the objects which abound with spontaneous light in a latent state, such as herrings, mackerel, &c., do not emit it when deprived of life, except from such parts as have been some time in contact with the air. Nor does the blast of a pair of bellows increase this species of light, as it does that which pro­ceeds from combustion.

IV. On the power of penetrating into space by telescopes; with a comparative determination of the extent of that power in natural vision, and in telescopes of various sizes and con­structions; illustrated by select observations

It will not be difficult to shew that the power of penetrating into space by telescopes is very different from magnifying power, and that, in the construction of instruments, these two powers ought to be considered separately. In order to conduct our present inquiry properly, it will be necessary to examine the nature of luminous bodies, and to enter into the method of vision at a distance. Therefore, to prevent the inaccuracy that would unavoidably arise from the use of terms in their common acceptation, I shall have recourse to algebraic symbols, and to such definitions as may be necessary to fix a precise meaning to some expressions which are often used in conversation, without much regard to accuracy.

IX. An account of a method of measuring the comparative intensities of the light emitted by luminous bodies. By Lieutenant-General Sir Benjamin Thompson, Count of Rumford, F. R. S. In two letters to Sir Joseph Banks, Bart. P. R. S

Dear Sir, About two years ago, being employed in making a number of experiments to determine, if possible, the most œconomical method of lighting up a very large workhouse, or public manufactory, which has been erected in the suburbs of this city under my directions, where the poor, old and young, and all industrious people who are in want of work, are employed in a great variety of different manufactures, a method occurred to me for measuring the relative quantities of light emitted by lamps of different constructions, candles, &c. which is very simple, and which I have reason to think perfectly accurate. I sent you a verbal account of this little invention about a year and a half ago, by Dr. Baader, who wrote to me that you seemed to be pleased with it; but, as I think it very probable, that he might not have been able to give you a complete idea of the matter from memory, I have determined to send you a short account of it in writing, which, if you should think it worthy of that honour, you will be pleased to lay before the Royal Society. The method is shortly this:— Let the two burning candles, lamps, or other lights to be compared, A and B, be placed at equal heights upon two light tables, or moveable stands, in a darkened room; let a sheet of clean white paper be equally spread out, and fastened upon the wainscot or side of the room, at the same height from the floor with the lights, and let the lights be placed over against this sheet of paper, at the distance of 6 or 8 feet from it, and 6 or 8 feet from each other, in such a manner, that a line drawn from the centre of the paper, perpendicular to its surface, shall bisect the angle formed by lines drawn from the lights to that centre; in which case, considering the sheet of paper as a plane speculum, the one light will be precisely in the line of reflection of the other.