very feldom faw one fmaller or larger than thofe limits, If, therefore, we take the fmalleft particles, and fet them in a row, we fhall find that about 3334 of them will equal one inch, and if we take the largeft, about 2500 of them will measure one inch.

When the particles are magnified more than 40 or 50 times, and lefs than 80 (meaning always in diameter) they appear like colourless tranfparent fpots incl fed within dark circles.

"When magnified more than 80 times, and lefs than about 160, a dark fpot, like a dot made with ink on paper, appears in the middle of each particle.

"If the reflector which illumines the particles, inftead of being fituated ftraight before the object, be fet on one fide of the axis of vifion, fo as to throw the light obliquely on the object, then the half of the dark circle of each particle difappears, viz. that half which is on the oppofite fide to the reflector. The central spot does at the fame time appear to change its place.

"When the particles are magnified above 200 times, the central fpot appears converted into a circle inclosing a tranfparent space. The diameter of this inner circle is about the half of that of the external one; but the proportion of thefe diameters, or the fize of the internal circle, may be caufed to increase or decrease by the least alteration of the diftance between the object and the microfcopical lens; and by the fame means the fpace within the inner circle may be rendered clearer or darker than that between the two circles. The position of the inner circle is changed by the direction of the light; for if the particle of blood be viewed through a microfcopical globule, directly facing the flame of a candle, without the intermediation of any lens or reflector, the inner circle will appear concentric with the outer one ; but if the candle be moved a little to one fide, fo that the light may fall obliquely on the particle of blood, then the inner circle will be obferved to move towards the oppofite fide, and to acquire an elliptical fhape.

"When the particles of blood are magnified above 400 times, an imperfect image of the candle, which is placed before the microscope, may be feen within the inner circle of each particle.

Through a glafs globule of 0,018 of an inch of diameter, I have feen the red particles of blood magnified about gco times, in which cafe the image of the flame of the candle could be feen within the inner circle of each particle very clearly, at leaft fo as to fhew to which fide the motion of the air in the room inclined it.

Notwithstanding this great magnifying power, the annulus or fpace between the two circles did not appear to be divided, excepting fome accidental fractures, which now and then could be seen in a few of the particies.

64

Thefe obfervations feem to prove, that the red particles of blood are not perforated, but that they are globular, and of fome uniform fubftance much lefs tranfparent than glafs. They likewife fhew that. Mr. Hewfon's idea of their containing a central body or nucleus, moveable within the external fhell, arole from the apparent change of place which the various direction of the light produces on the central fpot or inner circle of each particle. Warned, however, by the ex

ample

ample of other obfervers, I fhall not attempt to offer any further conjectures concerning the nature and conftruction of thofe particles. My reader may draw what conclufion he thinks proper from the abovementioned facts, and he may alfo, with little trouble, fatisfy his cu riofity concerning thofe appearances, as I find that microfcopal glafs globules may be had at Mr. Shutleworth's philofophical inftrument Thop on Ludgate Hill. I fhall therefore conclude with the account of a few experiments which I have made, with a view of imitating the phenomena that are exhibited by the particles of blood, the refult of which feems to corroborate what has been already obferved.

"On the fuppofition of the red particles being globular, I expected that globules of other tranfparent matter would exhibit the fame appearances as the particles of blood, and my expectations were in great measure verified by actual experiments.

"A glafs globule was placed as an object upon the stage of the microscope, and was fucceffively viewed through lenfes of various, but not great, magnifying powers. As every part of the globule could not be at once in the focus, the whole of it was not of courfe equally dif tinct. This indiftinction, however, being not very great, I fhall proceed without taking any farther notice of it.

"The globule appeared like a dark circular furface, with a tranfparent circular spot in the middle, and in this fpot there appeared a diftinct image of the candle or the window, or, in fhort, of any other object that was placed directly before it.

In this experiment three points of difference between the glass globule and the particles of blood were remarked, viz. 1ft, that the globule fhewed a diftinet, whereas the particle fhewed an indistinct image of the candle; zdly, that the inner circle of the globule is much smaller in comparison with its external boundary, than the inner circle of the particle is in comparifon with its external one; and, 3dly, that the annulus or fpace between the two circles is uniformly dark in the glafs globule, whereas in the particle it is about as clear as in the internal furface, or rather clearer.

"The first and the laft of thefe points of difference feem to depend on the imperfect tranfparency of the particles of blood; for in femitranfparent bodies, whatever light falls upon any part of them is fcattered through the whole body.

"The fecond point of difference I attributed to the particles of blood being furrounded by a coagulated fluid of nearly an equal re fracting power with themfelves, whereas the glafs globule was furrounded by air only. In order to verify this fuppofition, I placed the glafs globule in water, and viewing it in that face through the fame magnifiers that had been used before, I found that the transparent part or circle appeared much larger than in the former cafe.

"In the globule of glais, as well as in the particle of blood, the inner circle may be made to appear larger or finaller, by altering the diftance between the object and the microscopical lens.

"In the glass globule the inner circle may be feen to move from the middle of the dark furface, according as the candle is moved from the direct line between the object and the microfcopical lens." P. 247.

To

To what Mr. C. has faid refpecting the impoffibility of reftoring the globules to their former fhape, after having been dried, &c. we may add, that when they are dried on a piece of glass or tale, for microscopical obfervation, they do not feem, according to fuch experiments as we have made, to lose any thing of their natural appearance; except that they do not, quite fo diftin&tly as before, exhibit the central or feemingly included fpot; owing, probably, to their having affumed a degree of fatnefs in drying.

It would be injuftice to conclude this article, without obferving that the work appears to us, altogether, the most complete and fatisfactory that has yet been offered to the public, on the fubjects abovementioned; and well worthy the established reputation of the author.

ART. XIII. Phyfiology, or an Attempt to explain the Functions and Laws of the Nervous System; the Contraction of Mufcular Fibres; and the conftant and involuntary Actions of the Heart, the Stomach, and Organs of Refpiration, by Means of fimple, univerfal, and unvarying Principles. To which are added, Obfervations on the intellectual Operations of the Brain, and the Diverfity of Senfations, with Remarks on the Effects of Poifons; and an Explanation of the Experiments of Galvani and others on Animal Electricity. By E. Peart, M. D. 8vo. 327 pp. Miller, Old Bond-Street; and Murray and Highley, Fleet-Street. 1798.

T is even in thefe days fcarcely poffible to meet with a writer whofe prefumption reaches higher than that of the author of the prefent work, and whofe merit is at the fame time fo far be low the level to which he afpires. The contempt with which he treats the most rational, and the best established theories concerning the principal philofophical subjects, raises the curiofity of the reader to the expectation of fuch wonderful difcoveries, and fuch close reasoning, as may lead to more fublime and lefs equivocal refults. But we are forry to find that, inAead of new facts, and demonftrable conclufions, the book is full of indigested theories, and of difquifitions fcarcely rational.

The contents of the fixteen fections which form this work are pretty well announced by the copious title-page; but, with refpect to the quality of the materials, it would be equally ufelefs and tirefome to attempt their particular examination;

we

we shall therefore only select a few paffages for the fatisfaction of our readers.

In the Preface the author fays,

"That the chemical doctrines of Mr. Lavoifier, and the electrical theory of Dr. Franklin, are founded on abfurd principles, and are therefore erroneous, I have proved by fuch arguments as I do not for a moment hefitate to affert are abfolutely conclufive: whatever therefore may be the fate of my own theory, theirs, to a certainty, are falfe. With respect to my own principles, I feel as confident of their exiftence as of my own; how far I have fucceeded in developing the laws by which they are governed, is another matter; many of my conjectures may be erroneous, and much remains to be difcovered. Confidence, however, may be mifplaced; and I have all along declared, and ftill declare, that I would not for a moment hesitate to abandon both my theory and principles, were they once proved to be fallacious." Further on he fays,

"When I read, in every periodical work, from the Transactions of the Royal Society down to the humble Review, that the proud dia nond itself is nothing more than cryftallized charcoal,-what can I addbut, that when the readieft and beft method of thus cryftallizing charcoal is clearly pointed out, I will confefs that the discovery is as bril liant as it is wonderful! wonderful! wonderful!

According to the antiphlogistic fyftem, carbon, azote, and hydrogen, are three diftinct principles; but as each of them is capable of combining with the acid principle and of faturating it more or lefs completely; and as they are mutually convertible into each other, as is too well known to the antiphlogiftians to need infifting upon, 1 hefitate not to affirm, that they are one and the fame principle, in different ftates of purity, with refpect to the admixture of other matters, and with different proportions of the power by which they are rendered. atmospheric.'

Towards the end of the Preface he says,

"I by no means, however, offer this as a finished work upon the fubject; the refult of twenty years mature deliberation: on the contrary, I declare candidly, that it was began upon merely as a winterevening's amufement, and finished in less than twice the number of evenings."

After this laft declaration, we cannot help recommending to the Doctor, that he would allow himfelf more time to mature the productions of his luxuriant, but irregular imagination.

In the fecond fection, the Doctor gives the outline of his principal theory, which is as follows:

"Oxygen, or the acidifying principle, then, I shall call, for conveniency, the acid principle.

"Hydrogen, or the alkalefcent principle, I fhall diftinguish, by calling it the antiacid, or the alkaline principle; which, alfo, by partial

come

combinations with the other principle, and the powers in different preportions, forms the different kinds of earths.

"That peculiar power, or fluid, or principle, which renders the particles of the acid principle aeriform, by becoming atmospheric around them, I shall distinguish by the title of æther, or the ætherial power; and the fluid power, or principle, which, in an atmospheric ftate around the particles of the alkaline principle, renders them aeriform; I fhall call phlogifton, or the phlogiftic power.

"From the preceding confiderations, then, I draw the following general conclufions:

"1. That the brain confifts of two distinct substances; or different powers and properties: the cerebrum and cerebellum.

2. That they are intimately connected together, and invariably accompany each other, in all their ramifications.

66 · 3. 'I hat every common nerve is connected with the cerebrum and cerebellum; and therefore, that every nerve is compofed, in fact, of a branch from the cerebrum, and another from the cerebellum.

"4. That every branch of nerve connected with the cerebrum, contains and conveys a peculiar energy, fluid, or power; that every branch from the cerebellum contains and conveys a peculiar fluid, or power alfo; but effentially different in its properties from the former; and confequently, that every common nerve is composed of a nervous branch from the cerebrum, and another from the cerebellum; each of which is fupplied with its peculiar power, effentially different from the other.

5. That the heart and fanguiferous veffels contain and convey the blood; which is compofed of two diftinct principles, with their refpective powers in chemical combination.

"6. That the blood derives its principles and fupport, from the atmospheric air, conftantly taken into the lungs; and from the food repeatedly taken into the stomach.

66

7. That the principle taken from the air is the acid principle, rendered aeriform by the aetherial power.

8. That the principle selected and acquired from the food, is the alkaline, or antiacid principle, combined with a portion of the phlogiftic power.

66

That the blood, thus conftantly fupplied with the acid principle, with its ætherial power; and with the alkaline principle, with its phlogistic power; is capable, by co-operation with the nerves and their refpective powers, of producing all the functions of life; all the actions, and operations of the human fyftem."

In the other fections, and especially in that which treats of the intellectual Operations of the Brain, &c. this author is peculiarly confused. A numerous fet of undefining definitions, and references to conclufions which were never previously concluded, render the subject quite unintelligible to the reader, or we may at least say to us.

Upon the whole it feems, that the author is fuperficially acquainted with thofe fubjects, on which he attempts to write;

and