they can immediately form some judgement both of colours and distances, and even of the outline of strongly defined objects.

That when children have been born with cataracts, the crystalline humour has generally been found, either in a soft or a fluid state; and that in these cases, if the capsule be simply punctured with a couching-needle, there is reason to expect that the opaque matter will sooner or later be absorbed, and the sight be restored, and that should any opacity in the capsule itself render this operation ineffectual, the other, viz. that of extraction, may still be recurred to with every prospect of success.

Lastly, that this operation of couching being much more easy than that of extraction, it may be attempted at a very early period; and that thus the benefit of education may be afforded to children much sooner than if they were to wait till the proper age for extraction.

Mr. Ware acknowledges in a note, that about a month after the above operation he couched the other eye of his young patient, but that he did not prove equally successful: this he ascribes to some opacity in the capsule, which was incapable of being absorbed. The eye, however, he adds, remained as fit as ever for another operation.

An Account of some Galvanic Combinations, formed by the Arrangement of single metallic Plates and Fluids, analogous to the new Galvanic Apparatus of Mr. Volta. By Mr. Humphry Davy, Lecturer on Chemistry in the Royal Institution. Communicated by Benjamin Count of Rumford, V.P.R.S. Read June 18, 1801. [Phil. Trans. 1801, p. 397.]

Those who have attended to the latest experiments on galvanism, will recollect that the combinations hitherto used in that curious process consist of a pile of successive pairs of two metals, or of one metal and charcoal, and a stratum of fluid between each pair; and that the agencies of these combinations have been generally ascribed to the different powers of the metals to conduct electricity. Our author in the present paper states some arguments founded on experiments, from which it appears that an accumulation of galvanic influence, exactly similar to that produced in the above-mentioned pile, may be effected by the arrangement of single metallic plates, or arcs, between strata of different fluids. What first led to the discovery was the observation that the galvanic effects were readily produced when the metallic pairs were alternated with acids or other fluids capable of oxidating one only of the metals of the series. Double plates, for instance, composed of silver and gold, produced galvanic action when placed in contact in the common order with cloths moistened in diluted nitric acid; and plates of copper and silver when nitrate of mercury was used. It was hence inferred that galvanic effects might be produced if single metallic plates could be connected together by different fluids, in such a manner that one of their surfaces only should undergo oxidation, the arrangement in other respects being regularly progressive.

The first experiments were made with tin, small plates, or arcs, of which were made to alternate with acid and water. About twenty sets of these produce a galvanic battery, in which the wire from the oxidating surface of the plates evolved hydrogen, and that from the non-oxidating surface (when of silver) deposited oxide. The second series consisted of plates, or arcs, of silver, copper, or lead, placed alternately between cloths steeped in water, and in solution of sulphuret of potash. The effects of this combination were much more perceptible than those of the preceding. And a still more powerful battery was obtained by using metallic substances oxidable in acids, and capable of acting on solutions of sulphurets, and connecting them with oxidating fluids, and solutions of sulphurets of potash, in such a manner that the opposite sides of every plate may undergo different chemical changes. How this is to be effected is here explained at length, and an apparatus, contrived by Count Rumford, is lastly mentioned, for facilitating and giving permanency to the alternate succession of the different substances, so as to prevent, particularly in the fluids, the interference with each other, which would materially affect the results."

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. By Nathaniel Hulme, M.D. F.R.S. and A.S. Read June 18, 1801. [Phil. Trans. 1801, p. 403.]

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.

Oxygen gas does not act upon this kind of light so as to render it much more vivid than atmospherical air. And as to azotic gas, which is incapable of supporting light from combustion, it is remarkable that it should be so favourable to the spontaneous light emitted from certain fishes, as to preserve its existence and brilliancy when immersed in it, while it prevents the flesh of herrings and mackerel from becoming luminous, and extinguishes the light proceeding from rotten wood.

See Phil. Trans. for 1800, p. 161.

Hydrogen gas in general prevents the emission of spontaneous light, and also extinguishes it when emitted; but at the same time it does not hinder its quick revival when the subject of the experiment is again exposed to the action of atmospherical air.

The carbonic acid gas has also an extinguishing property; but in general the light will soon return if the subject of the experiment be replaced in the open air. Hepatic gas extinguishes spontaneous light much sooner than carbonic acid gas, and the light is much longer in returning when the subject is exposed in atmospheric air. Nitrous gas prevents the emission of light even to such a degree that a long subsequent exposure to common air cannot restore it. A vacuum suspends the emission of spontaneous light, but it returns immediately on the re-admission of air.

A few experiments on solar light, when imbibed by Canton's phosphorus, are here subjoined, from which we learn in general that this light is subject to the same laws with respect to the influence of heat and cold, as the spontaneous light of fishes, rotten wood, and glowworms, of which an ample account is contained in the author's paper on this subject, already published in the Transactions.

Experiments on the Chemical Production and Agency of Electricity. By William Hyde Wollaston, M.D. F.R.S. Read June 25, 1801. [Phil. Trans. 1801, p. 427.]

The power of Professor Volta's pile to produce galvanism is now supposed to depend on the disposition of one of the metals employed, to be oxidated by the fluid interposed; but a doubt is still entertained whether that oxidation depends on electricity set in motion by the contact of the metals, or whether the electricity be excited by some chemical action of the substances used. The experiments described in the present paper seem to favour the latter opinion, viz. that a chemical agency is the cause of the effects produced.

They go principally to prove that this chemical agency of common electricity is the same as the power excited in Professor Volta's apparatus, likewise by chemical means. The production of airs by the electric pile is here imitated, and even the appearance of two currents is produced, by occasioning the electricity to pass by fine points of communication on both sides of the water at the same time, each wire yielding both hydrogen and oxygen gas.

It is also observed, that in the same manner as in Professor Volta's apparatus, there is manifestly a disposition to oxidate on the positive side alone; and that although oxygen gas be given as well as hydrogen by the negative wire, that wire is never perceptibly oxidated; while the positive one, when of silver, uniformly shows a stream of oxide proceeding from it. This is accounted for by the supposition that the difference between these two effects is owing to the greater intensity of common electricity in the method hitherto employed; and it is ultimately inferred that galvanism probably differs solely in quantity and want of intensity from common electricity.

Further Observations on the Effects which take place from the Destruction of the Membrana Tympani of the Ear; with an Account of an Operation for the Removal of a particular Species of Deafness. By Mr. Astley Cooper. Communicated by Everard Home, Esq. F.R.S. Read June 25, 1801. [Phil. Trans. 1801, p. 435.]

The former part of this paper may be considered as a continuation of a preceding one by the same author, printed in the last volume of the Philosophical Transactions, and contains an enumeration of many more facts and circumstances, from which we gather that an aperture in the Membrana Tympani does not essentially diminish the power of the ear, and that even a complete destruction of that membrane is not followed by total deafness.

The causes by which it may be injured are here further inquired into, and are found chiefly to be a suppuration in the Meatus Auditorius, and any kind of external violence; such as blows on the side of the head, the forcible introduction of extraneous substances into &c.

the ear,

Mr. Cooper proceeds next to describe the remedy he has, in consequence of his repeated observations that an aperture in the Membrana Tympani does not injure the ear, thought fit to apply to one particular species of deafness; namely, that which arises from an obstruction in the Eustachian tube. After enumerating the causes which most frequently produce these obstructions, such as colds, which often affect the parts contiguous to the orifice of this tube, ulcers in the throat, extravasation of blood, and uncommon strictures in the tube, the author proceeds to describe his operation, which consists simply in puncturing the membrane, with very little pain to the patient, and with instant relief to the disorder.

Several cases are described in which the operation has proved successful.

The criteria are next mentioned by which it may be known whether this tube be closed or open: and lastly, those kinds of deafness are enumerated in which the operation is not likely to produce any salutary effect. These are, when the auditory nerve is affected; when there is any alteration in the contents of the labyrinth; and when in general any derangement takes place which does not immediately affect the Eustachian tube.

The Croonian Lecture. On the Power of the Eye to adjust itself to different Distances, when deprived of the Crystalline Lens. By Everard Home, Esq. F.R.S. Read November 5, 1801. [Phil. Trans. 1802, p. 1.]

Its object is to state some facts and observations in support of an opinion advanced by the author in a former Lecture, that the adjustment of the eye to see objects at different distances does not depend upon any internal changes in the crystalline lens.

Before he proceeds, Mr. Home pays a due tribute of praise and

gratitude to our late ingenious brother, Mr. Ramsden, to whom he says he is chiefly indebted, not only for the information which was necessary to enable him to prosecute his investigations upon the subject of vision, but also the zeal which influenced his early exertions in the philosophical career.

The opinion here alluded to was brought forward in Mr. Home's Lecture for the year 1794, and was founded upon experiments which seemed to prove that the removal of the crystalline lens does not deprive the eye of the power of seeing distinctly at different distances.

An additional case is here mentioned of a man who had a cataract extracted from each of his eyes, and yet preserved a considerable range of vision.

In the Bakerian Lecture of last year, Dr. Young, having entered minutely into the inquiry, thought himself authorized to doubt the above inference; and in order to insure the accuracy of the experiments he intended to make on the subject, he constructed an optometer upon the principle of that of Dr. Porterfield, by which he could ascertain the different focal lengths, and hence the power of adjustment of every eye. The result of his experiments was, that eyes deprived of the crystalline lens have lost their power of adjustment.

This difference of results induced Mr. Home to reconsider the subject, and having sent for the man from whose eyes he had last extracted the cataracts, he repeated the experiments with Dr. Young's optometer, somewhat simplified by leaving out the lens which was placed before the eye. With this instrument that man was unquestionably found to have distinct vision at different distances, the nearest focus being at only 8.3 inches, and the furthest at 13.3 inches, while with Dr. Young's optometer he could never observe any dif ference whatever.

Besides this individual, others, whose eyes had never been disordered, tried the effects of both optometers; and it should seem, from the various impressions produced upon them, that the contradiction in the above results depends chiefly, if not entirely, on the difference of the instruments.

The Bakerian Lecture. On the Theory of Light and Colours. By Thomas Young, M.D. F.R.S. Professor of Natural Philosophy in the Royal Institution. Read November, 12, 1801. [Phil. Trans. 1802, p. 12.]

Although the mode, much practised by the ancients, of accounting for a variety of phænomena by a preconceived hypothesis, be, if not wholly exploded, at least greatly discountenanced by modern philosophers; yet it must be owned that when a number of facts have been collected and duly ascertained, it cannot but be conducive to the extension of knowledge, to arrange them under certain heads, and, if possible, to ascribe them to some general cause; and that with men who are candid and not over-tenacious, even an error in