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The treatise is divided into seven books. The first book is entitled, "Of general Phenomena, and of the Means of making Observations;" in which, after some remarks upon the nature of matter, the definitions that have been given of it, both physical and metaphysical, we have an account of its essential properties, and the effects necessarily resulting from them. This leads to the method by which these properties are to be ascertained, and their amount measured, by means of certain operations, and of peculiar instruments, which are detailed and described. The titles of the chapters which compose the first, Dook are as follows: Of the Balance, and the Manner of using it; of the Construction of the Thermometer, and the Manner of using it; of the Destruction and Reproduction of Heat which are observed during the Change in the State of Bodies; of the atmospherical Pressure, and of the Barometer; Relations of the Barometer and the Thermometer; Laws of the Condensation and Dilatation of Air and the Gases, under different Pressures at the same Temperature; of Pumps, both for Fluids and for Air; Measure of the Dilatation of solid Bodies, of Gases, and of Liquids, by Heat; Laws of the Dilatation of Liquids at all Temperatures; of the Forces which constitute Bodies in the different States of Solids, Liquids, and Gases; of Vapours in general, particularly of their Formation, and of their elastic Form in a Vacuum; of the Method of measuring the Weight of Vapours under a given Volume at a determined Pressure and Temperature; of the Mixture of Vapours with Gases; of Evaporation; of the Hygrometer; of the Specific Gravity of Bodies; of the Means of obtaining the Specific Gravity of Bodies; of Capillary Phenomena; and of Elasticity.

The second book is on acoustics, a subject naturally connected with the last chapter of the former book, consisting of the peculiar effects which elastic bodies produce on one of the organs of sense. The second book is divided into 13 chapters, under the following titles: of the Production and Propagation of Sound; of the Perception and Propagation of continued Sounds; the usual Approximations in Music to express the Intervals of Sounds; Necessity of altering the Adjustment of these Intervals in Instruments with fixed Notes; Rules for this Temperament; transverse Vibrations of straight elastic Rods; longitudinal Vibrations of straight Rods; circular Vibrations of straight Rods; of the Vibrations of curved Rods, such as Forks and Rings; Vibrations of Bodies rigid or flexible, moved in all their Dimensions; of wind Instruments; on the Vibrations of acriform Fluids different from Air; on the Reverberations of Bodies; Organs of hearing and speaking.

Before entering upon the third book, which is on electricity, M. Biot observes, that the properties of bodies about which he has hitherto been treating, are constantly inherent in them, and seem to be essentially attached to the matter of which they are

composed. Heavy bodies, for example, cannot be deprived of their weight, nor their particles of the property of mutually attracting each other. There are, however, other kinds of qualities, which may be impressed upon bodies in a more transient manner, and which are developed in them, without the addition, so far as we can judge, of any tangible or ponderable principle. In treating of electricity, the first of the qualities or modifications of the kind here referred to, the author first lays down its general laws as they are ascertained by observation and experiment; then from these he deduces his theory, and afterwards describes the various kinds of apparatus. The number of chapters is 20, and they bear the following titles: general Phenomena of electrical Attractions and Repulsions; Distinction of the two Kinds of Electricities; of the Laws which the apparent Attractions and Repulsions of electrified Bodies follow; of the Laws according to which Electricity is dissipated by the Contact of Air and the Supporters which retain it imperfectly; Disposition of Electricity in Equilibrio in insulated conducting Bodies; of combined Electricities, and of their Separation by Actions without Contact; Theory of the Motions excited in Bodies by electrical Attractions and Repulsions; of the best Construction of electrical Machines, and the Conductors which form Part of them; of Electroscopes; of what are stiled Electricités dissimulés, under which are included the Condenser, the Electrophorus, the Leyden Jar, and electric Batteries; of electric Piles, and of the Phenomena which Crystals electrified by Heat present; Applications of Electricity; mechanical Effects produced by the repulsive Force of accumulated Electricities; of atmospheric Electricity, and Conductors for Lightning; of electric Light; of the Development of Electricity by simple Contact; Theory of the electromotive Apparatus, supposing its conducting Power to be perfect; chemical Effects of the electromotive Apparatus; Theory of the electromotive Apparatus, considered with regard to its imperfect conducting Power; Examination of the Changes which take place in the electromotive Apparatus in consequence of its Re-action upon itself; Modifications which result from its electric State; of secondary Piles; on the unequal Resistance which the two Electricities experience in crossing different Bodies, when they are very feeble.

Magnetism forms the subject of the fourth book. The following topics are discussed in it: general Phenomena of magnetic Attractions and Repulsions; general Considerations upon the Development of Magnetism in magnetic Bars, and their Analogy with electric Piles; Determination and Measure of the directing Forces exercised by the terrestrial Globe upon Magnets; upon the different Ways of magnetizing; general Distribution of Magnetism in Bars by the double Touch; Laws of magnetic Attractions and Repulsions; Research into the Intensity of free Magnetism in every Point of a Needle saturated by Means of the

double Touch; of the Influence of Temperature upon the Development of Magnetism; of the best Form for Compass Needles; of the Action of Loadstones upon all natural Bodies; Laws of terrestrial Magnetism at different Latitudes.

The fifth book is on Light: it is divided into the three parts of catoptrics, dioptrics, and the analysis of light. Under catoptrics we have the general Laws of the Reflection of Light; of the plain Mirror; of curved Mirrors; of the Heliostate, and general Considerations on the Forces which produce the Reflection of Light at the Surface of Bodies. Under dioptrics we have general Laws of simple Refraction; of spherical Lenses; physical Theory of Refraction; of double Refraction; Construction of Micrometers with double Images. The analysis of light embraces the following Topics: of the Dispersion of Light produced by Refraction; Influence of the unequal Refrangibility of the Rays upon Vision across refracting Surfaces; of Achromatism. In a sequel to the subject of dioptrics we have six chapters on the following subjects: on the Reflections, Refractions, and Colours, of thin transparent Bodies; on the Fits of easy Reflection and easy Transmission; Application of the preceding Theory to the Reflection of the Rays of Light which have crossed thick Media; Explanation of permanent Colours of Bodies; on the Return of Rays reflected by Plates with plain and parallel Faces; on the Return of Rays by curved Plates; Explanation of the coloured Crowns which appear round the Stars; on the Colours produced by many successive Reflections; what takes place when Colours reflected or transmitted by thin Plates seem to emanate from their Substance.

The polarization of light is become quite a new science, and accordingly forms the subject of the sixth book. The following are the titles of the chapters that compose it: general Proceed ings by which we produce permanent Polarization; of the Periods in which Polarization is produced and completed in crystallized Bodies possessing double Refraction; of the Colours given by thin crystallized Plates, when we present them to Rays under certain Incidences; experimental Laws of these Phenomena; oscillatory Motion of the Axis of Polarization deduced from the preceding Phenomena; Examination of the Modifications experienced by the Molecules of Light, when they cross many Plates in Succession, which produce the moveable Polarization; Processes which result from them to develop coloured images in thick Plates by the crossing of their Axes; of the physical Properties which the Molecules of Light assume in the Interior of Crystals; critical Examination of the Phenomena produced under oblique Incidences by Lamina and Plates parallel to the Axis of Crystallization; Experiments upon Plates of Rock Crystal cut perpendicularly to the Axis of Crystallization; Phenomena of successive Polarization observed in homogeneous Fluids; Examination and Laws of the Phenomena which Plates

of Mica present under oblique Incidences; Phenomena of Polarization which are observed in Bodies imperfectly crystallized; Determination of the Laws according to which Light is polarized at the Surface of Metals.

The seventh and last chapter is on heat, both radiant and latent; it contains the following topics: on the Relations of Light and Caloric; Laws of the heating and cooling of Bodies in undefined Media; Influence of the State and Nature of Surfaces upon the Radiation of Caloric; Theory of its Equilibrium by mutual Exchange; Laws of the Propagation of Heat in solid Bodies; of the Capacity of Bodies for Caloric; and of Steam-Engines.

This very ample table of contents will afford a clear proof of the extensive view which M. Biot has taken of natural phenomena; and the manner in which he has treated all the different topics equally prove the profound and elaborate spirit of philosophical investigation for which this author is so justly distinguished. There is a general air of candour pervading every part of the work, which is highly creditable to the author; and an appearance of dispassionate good sense, which produces a feeling of confidence in all his statements. Different persons, according to their turn of mind and previous pursuits, will form different opinions respecting the propriety of introducing so much of mathematic and algebraic reasoning; but, admitting the principle, the execution is highly commendable. The arrangement of the materials is good, and its stile perspicuous; and it has very little, if any, of the obscurity which so frequently pervades works of science, arising from the fanciful introduction of new terms, or the no less fanciful employment of old terms in new senses. Many readers will regret that M. Biot has not given more of a regular historical detail in connexion with the different topics on which he treats. It no doubt adds much to the interest of works of this description, and seems a kind of tribute due to our precursors in science. M. Biot seldom refers to the labours of preceding authors, except in an incidental manner, and does not seem to have conceived it a part of his plan to state by whom the knowledge that we at present possess was originally discovered.

ARTICLE XII.

Proceedings of Philosophical Societies.

ROYAL SOCIETY.

The Society met on Nov. 6; but, in consequence of the death of the Princess Charlotte of Wales, the meeting was adjourned. Nov. 20.-Sir Everard Home read the Croonian Lecture, the

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subject of which was the changes which the blood undergoes in the act of coagulation. A considerable part of the paper consisted of an account of a number of minute microscopical obser vations that had been made by Mr. Bauer, on the red particles of the blood. He attempted to form an estimate of their size, and gave a description of their appearance. Their colouring matter he conceives to be something superadded to their proper substance he supposes that they possess a regularly organized structure; and by comparing them with the appearance which the muscular fibre exhibits, when highly magnified, he concludes that these particles are the immediate constituents of the fibre. With respect to the generation of vessels in effused blood, he imagines that it depends upon the gas which is extricated from blood during its coagulation: this, by insinuating itself between the adhering particles, produces tubular cavities, which are afterwards converted into more perfect vessels.

November 27.-A paper by Mr. Seppings was read, on the increased strength given to ships of war by the application of diagonal braces. It contained an account of some very ample trials that had been made of this method of constructing the framework of vessels, the result of which was such as completely to justify the expectations that had been raised, and to confirm the favourable reports that had been made on the subject.

On Monday, Nov. 31, the Society held its annual meeting, for the election of the officers for the ensuing year. There were elected,

President.-Right Hon. Sir Joseph Banks, Bart. G.C.B. &c. Secretaries.-William Thomas Brande, Esq. and Taylor Combe, Esq.

Treasurer-Samuel Lysons, Esq.

There remained of the old council: Right Hon. Sir Joseph Banks, Bart.; William Thomas Brande, Esq.; Samuel, Lord Bishop of Carlisle ; Taylor Combe, Esq.; Sir Humphry Davy; Sir Everard Home, Bart.; Samuel Lysons, Esq.; George, Earl of Morton; John Pond, Esq.; William Hyde Wollaston, M.D.; Thomas Young, M.D.

There were elected into the council: George, Earl of Aberdeen; Davies Gilbert, Esq.; Charles Hatchett, Esq.; Captain Henry Kater; William, Lord Bishop of London; Right Hon. Charles Long; John Reeves, Esq.; Richard Anthony Salisbury, Esq.; Edward, Duke of Somerset; Glocester Wilson, Esq.

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Since the last anniversary 21 members have died, one has withdrawn, and 25 new members have been admitted. present number of members is 652, of which 40 are foreign members.

The Copley medal was adjudged to Captain Henry Kater, for his experiments on the length of the pendulum vibrating seconds. On Dec. 11, a paper by Capt. James Burney was read, on the geography of the north-eastern part of Asia, and particularly

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