Imágenes de página

Lurope. It is the national character of the French ;-as' masters or rivals, their vanity is insupportable ; as dependants or inferiors, they are atten, tive and accommodating: they were born to obey, not to command."

His estimate of the French character is perfectly just ; but we dare not encourage the hope that the empire of Buonaparte will speedily crumble away. To reason, however, froin the past to the future, notwithstanding the futility of such a inode of argument as applied to recent events, is certainly fair, and experience fülly sanctions the conclusions of our author.

The notes, Greek, Latin, French," Spanish, Italian, and English, display a great extent and variety of reading, without any affectation, or ostentatious parade of learning; and the tract, on the whole, is highly creditable to the author's abilities and principles.

Lectures on Natural Philosophy : the Result of many years praftical

Experience of the Faets elucidated. With an Appendix, containing a great Number and Variety of Astronomical and Geographical Problems : also some useful Tables, and a comprehensive Vocabulary. By Margaret Bryan PP. 420. 40. Kearsiey. 1806.

PASSIONS, prejudices, or prepossessions, have hitherto influenced the opinions of men, in whatever relates to the female character. It is therefore extremely difficult, if not impossible, to use language that will impress all readers with a just idea of the intrinsic value of any production of the female mind. If we express an ingenuous approbation of such a production, those who think their own consequence ‘raised by depreciating every thing which originates with the sex, will uncandidly exclaim, it is very well for a woman! If, on the contrary, we dwell more on che defects than the merits of the work, the sex has just reason to complain of partiality. Since, then, the generality of readers are more apt to be interested in the superficial question relative to a supposed sexual characteristic of the mind, than to dispašsionately appreciate the importance and accuracy of the information contained in the works of a female writer, we shall endeavour, justitiaque dedit gentes frænare super bas, to convince our readers, that it is not of authors, but of their works, that we are called upon to give our judgment; and that to us is is perfectly indifferent, whether the volume before us was written by a male or a female-it is the principles alone we shall consider. Nor do we, as critics, know any sex

in writers ; the genius of our language, iis admirable simplicity, réjects all sexual terminology, which is common to almost every other known language ; and although custom has reconciled us in some de. gree to the barbarous terms of authoress, precepiress, &c. there is no person who could bear such wors as writreis, paintress, &c. ; yes if it were necessary to characierize iniellectual agency by any sexual rer'pination, it is equally, so in the intier case as in the format. Leaying,



however, such discussions

for the present, we shall proceed to tu ana. lysis of these Lectures on Natural Philosophy.

The volume before us contains Thirteen Leatures on the Properties of Matter, Mechanics, the Properties of the Atmosphere, Pneumatics and Acoustics, Hydrostatics, Hydraulics, Magnetism, Electricity, Optics, the Nature of Light and Vision, and on Astronomy. To chese is added a very copious Appendix, consisting of astronomical tables, specific gravities, geometrical definitions, the most remarkable stars and constellations seen in the zenith of London, principles of the globes and arıilláry sphere, with numerous well-conceived geographical problems and questions, designed to exercise the students of geography and astronomy. I cannot be expected that, in creating of such subjects, which have long been stationary in the annals of science, much novelty should now be attained. It is not, however, that these sciences have been carried to perfection, but that they have arrived at a certain point, to surpass which, it will require the collected experience of another century to be concentrated in some original and aspiring genius, who may be fortunate enough to extend our knowledge of the natural sciences beyond the limits to which they at presene appear circumscribed.

Nevertheless, although the mathematical principles of mechanics, hydrostatics, and pneumatics, have become Stationary, new discoveries in their application to the arts daily occur ; and it will appear, that our author has been fortunate in introducing her due portion of new and appropriate illustrations of these wellknown principies. In the First Lecture, after treating on fire, and its agency, the following, among many other, observations on evaporation appear :

The cooling property of vapour is evident by the observation of its effects, and the manner in which they are employed in hot countries. In Aleppo, water kept in jars is always coolest when the weather is hottest: for when the heat is most excessive, and the sun's rays most powerful, the vapour from the outside of the jars is most copious; and the degree of coldness within them is produced by the great quantity of heat discharged through the pores of the earth of which they are made, which is of a very loose texture. The manner of obtaining ice in the East Indies is another evidence of the degree of cold that may be produced by evaporation. The ice makers dig pits about thirty feet square and two feet deep, in large plains, strewing the bottom of these pits with sugar-canes : rhey place upon them unglazed pans, made of such porous earth, that the va. pour penetrates through its substance. The pans are about a quarter of an inch thick : if they are filled in the evening with water that has been boiled, and left in that situation till moming, more or less ice will be found in them, according to the temperature of the air, there being more formed in dry weather than in cloudy.

As the above conveys the knowledge of an inportant fact, which seems not to have been yet sufficiently known or practised in many of those warm countries which are under the British dominion, and which frequently suffer from the use of bad water, we think it pro



per to observe, that even Hot and muddy water, put into a thin, porous, unglazed earthen vessel, and suspended in an open window, or any place where there is a constant current of air, shaded from the sun, will, in the course of six or seven hours, become cool, limpid, and a delicious and wholesome beverage. The same may be effected with large jars exposed to the sun ; but in that case it is necessary to keep them close stopped, and constantly moistened with water thrown over them, in order to support a uniform evaporation from their sur, face. Our author's hypothesis, that in this process of evaporation, heat is disengaged, may suffice, although many, and not without reason, have contended, that the matter of heat was carried off in vapour, and that of cold disengaged in a quantity sufficient to cool, or even freeze, the water within the vessels.

In the Second Lecture, treating of the mechanical powers, the aui thor remarks ; “ The effects of gunpowder are certainly dreadful; yet as some mediuın (mcans) of offence and defence has ever been used, I conceive the art of gunnery is not more cruel than-many other destructive devices.” How little do we yet know of humanity! In truth, after the discovery of printing, that of gunpowder has been the next useful in civilizing mankind, and in extending the arts and sciences. As to the sentiment of humanity, if there be any cruth in the records of society, we have but to compare the history of ancient and modern wars to be convinced, that since the use of gunpowder, scarcely a hundredth part of the former number has fallen in battle. The period of warfare has been also contracted, and the arts of peace cultivated to a degree equally unknown in ancient Rome, Greece, Judea, or Egypt. There is, however, more justice and utility in the following interesting observations on animal strength: !

« It appears evident, from what we learn of the direction of power in the limbs of men and quadrupeds, that the former were designed to move upright, and that they can bear a burthen better in that position than in any other. Two men with a burthen between them, will carry a greater weight than double what each can separately; because by using a pole, they can preserve such a position that the whole pillar of their bones sup. ports the weight. If one man be twice as strong as the other, the weight should be moved towards the stronger man in that proportion, namely, to half the distance from the latter that it is from the former; by which means the weaker man will bear only one-third of the burthen. In at. taching a pair of horses to a carriage, if one be weaker than the other, the stronger horse should be placed nearer the centre of the beam that is fastened to the carriage, than the weaker, by which means each will draw in proportion to its strength; the motion of the carriage will also be facilitated by this equipoise of power.

“ We may infer from the direction of power in horses, that they were designed to draw burthens ; and may suppose that a horse will draw a weight in proportion to his strength : yet it is easy to understand, from our observations on action and re-action, that 'two horses of *unequal strength may draw the same weight; or the weaker horse may even draw

a weight

[merged small][ocr errors]

2 weight the stronger cannot remove, if the weaker be the heavier, of exceed the other more in weight than he is exceeded by him in strength for a weight re-acts and pulls back a horse in proportion to itself: there fore the heavier horse, though he be the weaker, will, if his weight be greater than the strength of his antagonist, lose less power than the stronger one. A horse has two sources of power in drawing weights': his strength, which gives him velocity; and his weight, which gives him force. Horses must have suficient force, or weight, to enable them to move a heavy carriage ; for if they have not, they cannot secure their feet on the ground, but will slip, and be drawn backwards."

The Lecture on Pneumatics and Acoustics is still more comprehensive and instructive, although the author has declined entering on the enchanting and fashionable subject of pnevinatic chemistry, under she false pretext, that the “ experiments are too inconvenient and dangerous for female * performance and introspection.” She illos. grates the importance of the existence of the air to the feathered tribe, whose small heads, sharp breasts, muscular wings, and spreading tails, enable them to support theinselves in the atmosphere. But,

« The re-action of the air alonc is not sufficient to account for the direction, &c. of the fight of birds : it is by the curious mechanism of their wings that they are able to support themselves, and to vary their fight, as we may readily conceive ; for if it were performed and effected by strokes in one plane only, what was gained one moment would be lost the next. But the wise Contriver of all things has supplied the plamy Tace with a curious and wonderful machinery to effect these purposes. The external part of the wing is convex, and the feathers are so disposed, the muscles and joints of the pinions so arranged and allotted, as to enable birds to shift their position by a semi-rotary movement, and also to strike the air with a broad surface, in order to take all possible advantage of its sesistance ; and to raise the wing edgeways, that they may have the less opposition to overcome, and to prevent that action of the air on thens in rising which would impede their Hight: it was probably from observing this circumstance, that the waterman learnt what is called to feather his par."

After discussing the important uses of air to the respiration f of animals, the lecturer proceeds to consider its wonderful powers in propagacing sounds.

The yery able researches and discoveries of Mrs. Fulham, are a satis, factory refutation of this objection.

The author again attacks experimental philosophers for cruelty to ani mals, in exposing them to the action of diferent gases; but she does noc teflect that there is not a respectable fishmonger in London, who does not inflict more cruel torture on living animals in one day, than all the philo, sophers, from Galea to. Galvanhiie cver done in the course of their lives,


“ Sound, by being condensed in a tube, is rendered audible at a great distance; therefore, by means of pipes, which confine the sound, the voice may be heard considerably beyond its natural limits. Hence have arisen various deceptions. The condensation of sound has similar effects with the condensation of light, in increasing the natural powers. When a person speaks in a trumpet, the large waves formed at the wide end of it are compressed at the axis by the reflecting surface inside the tube ; and, passing to the ear in that state, a greater effect is produced than by the usual mode of conveyance. If two trumpets are fixed in situations oppo. site to each other, even at the distance of forty feet, the sound of the lowest whisper spoken at the mouth of one of them, will pass to the other, and may be distinctly heard. The similarity between the effects of con. densed light and sound is evidently proved by experiment. If we place two concave mirrors, or surfaces, made of glass, or any reflecting substance, at the opposite ends of a large apartment, and a person stand at the focus of one *, and another person at the focus of the other, they may converse in the lowest whisper, which will be to each perfectly au. dible.”

The Fifth and Sixth Lectures are devoted to the illustration of hydrostatics, hydraulics, and the notion of fluids in general, of which the following is a fair speciinen of the diverse facts and observations communicated in the author's familiar and desultory manner :

“ The effects of capillary attraction, by which moisture is conveyed through the interstices of wood, &c. are employed by mankind in various mechanical operations, particularly in dividing substances with greater ease and safety than by percussion. A very striking use of this property presents itself to my recollection, as ernployed in dividing mill-stones. The stones used for this purpose are first formed into cylinders of considerable length; to separate these into the proper proportions, indentures are cut at suitable distances on the outer surface of them in a circular form, into which are driven wedges of dry wood. By the application of water to these wedges, the cylinders are divided; for the Auid is drawn to the other extremity of the wood by the capillary attraction, which causes an expansion that splits the stone asunder. Capillary attraction is concerned in most of the operations of nature; for nutriment is conveyed through these fine tubes to all the parts of vegetable substances and animal bodies. Many familiar effects arise from corpuscular attraction; as, oil supplying the wick of a lamp, water dividing sugar or salt: in a word, all the pores and interstices of bodies are capillary tubes, which imbibe Auids, efflu. via, &c."

The Lecture on Magnetism is the most intelligible, satisfactory, and perhaps complete, that we have seen on this hitherto undefinable subject. The author has evinced much judgment and good sense in omitting all the visionary speculations relative to magnetism, with

* “ The focus of a concave mirror is at one fourth the diameter of a sphere of which the concavity of the mirror is an arc.".


which NO. CII. VOL. XXV.

« AnteriorContinuar »