difcipline, without laws. In the reign of Fou-hi, they are reprefented as a civilized, intelligent, refined people, skilled in fcience, acquainted with the mode of computing time by a cycle of fixty years, obfervers of the celeftial figns, and the motions of the heavenly bodies. The art of writing is faid to have been invented in the reign of Houng-ti, many aftronomical obfervations made; the folar and lunar years nearly adjusted, the motions of the planetary orbs determined, an Orrery conftructed, &c. Within the space of a century after the death of Houng-ti, we are told, that the Chinese were fo profoundly skilled in aftronomy, as to calculate a conjunction of the planets which happened in that period. Other inftances of their uncommon penetration and abilities in thefe early ages might be mentioned: but I proceed to obferve, that the account of the ra pid progrefs of the Chinese to perfection in science, does not accord with our notion of the improvement of the human mind, with the ftate of fociety in its earliest period, with the national character of the Chinese themfelves, nor with other parts of their history. The improvements of nations, as well as individuals, is gradual, being the refult of many vigorous, and often painful efforts. No where elfe have we found that a people had arrived at perfection in the fpeculative and abstract fciences, while they remained in a state of immaturity with refpect to the useful and ornamental arts: nor has any inftance been produced, in which a nation has gradually relapsed into ignorance of a fcience in which they had been thoroughly verfant, while the fame means by which they originally acquired knowledge have been regularly ufed, and while they made uniform, though flow progref, in other branches of fcience, and in the arts. Farther, if we look into the first period of the Chinese history, and take a view of their manners, customs, &c. as therein reprefented, we must observe, that their improvement in the neceffary and useful arts was, for many ages, inconfiderable, and not fuited to those who had attained to perfection in the fublimer fciences. It may be added, that their national character has always oppofed the idea of rapid progrefs in literary pursuits. They are flow and fuperficial, deftitute of fubtlety and penetration, without invention, without curiofity, without enterprize. Accordingly we find, that though for the space of feveral thousands of years focieties have been established for literary purposes, and recompences have been bestowed on learned men, yet the empire of China has not produced a fingle man of great attainments in fpeculative fcience, nor one who has difplayed that degree of acutenefs and penetration that is effential in the study of phi lofophy, or the defire of information neceffary to improvement in knowledge. From these particulars it is very obvious, that there is some reason for calling in queftion the authenticity of the ancient Chinese annals and historical books.'

The high antiquity of Egypt is examined with the fame care, and rejected with the fame probability. And indeed, at a time when it has become fashionable, even for philofophers, to extend the duration of the world beyond the limits to which ignorance and pride had carried it, we cannot help commending Our Author's moderation and judgment in defending that fyftem

which is deduced from the authority of fcripture, and preferring the teftimony of Mofes, to the fplendid but precarious reasonings of Bailly and Buffon.

In the modern part of universal history, our Author has lefs occafion for deep research into points of chronology. But here too we find the fame judicious arrangement, the fame perfpicuity and fimplicity of narration, which diftinguishes the whole of the work. The felection of facts is every where happy; and though the fcale on which the hiftory is written is enlarged as it approaches the present times, this occafions no difproportion in the parts, but rather gives to the whole an air of perfpective natural and pleasant.

Next follows a catalogue of eclipfes, containing a lift of all that have happened from the birth of Chrift to the present times, computed from the tables of modern aftronomy. A short defcription of the phenomena of each eclipfe is joined to it, which, together with a table of the limits of eclipfes, to be found in the Appendix, enables us to form a very tolerable idea of the appearance of any one of them at any affigned place. This is of infinite ufe in chronology as well as in geography. The table is adapted to the meridian of Paris, and, as our Author tells us, has been extracted from the celebrated work intitled, L'ART DE VERIFIER LES DATES.

The table of eclipfes is followed by a chronological lift of councils, containing the title and date of every council, toge ther with the chief subject of debate. For what reason these two tables are brought fo near each other, we are at a loss to conje&ure, unless our Author meant to infinuate, that councils and eclipfes have both occasionally spread darkness over the face of the earth. It will furprize a reader not acquainted with ecclefiaftical history (the blackest part of the annals of human frailty), to be informed, that it has required upwards of 1600 of these councils, notwithstanding the infallibility of each, to regulate the faith and difcipline of the church.

The fourth part contains the chronological tables and charts, which unite the advantages of the plans of Dr. Blair and Dr. Priestley. The defign of them, our Author fays, is to exhibit a representation of the reigns of kings and emperors, and of the lives of remarkable men in all ages, together with the years of every important æra, from 2200 B. C. to the prefent time. This period is divided into equal portions, every one of which confifts of 600 years. Each page contains the years, lives, or reigns, relating to the interval fpecified in the title prefixed.

Each page is interfected by perpendicular and horizontal lines. The pace contained between the latter represents centu ries of years; and all that is included in the fame space refers to the fame century, whether it be the reigns of kings, the years

of different æras, or the lives of eminent men. The tables of reigns and of æras are alfo divided by horizontal lines into half centuries, in order to affift the eye in the obfervation of correfponding years.-The feveral fpaces bounded by perpendicular lines include what relates to the feveral claffes or denominations indicated in the title and contents of each page. The marginal perpendicular line is divided into a fcale of years, for the ufe of the tables. Half a century of this fcale is fubdivided into fingle years, and the remaining centuries into intervals of five years. The perpendicular fpace on the left hand of each table contains the reigns of kings. The dates and duration of these reigns are marked by fmall afterifks prefixed to the name of each king. Thefe marks may, with eafe, be referred to the marginal fcale, by means of compaffes, or a parallel ruler.

The great advantage of the charts, each of which, though confifting of three parts, folds out fo as to be all under the eye at once, is, that they reprefent to fenfe and imagination the fucceffion of thofe men, who from their fituation or abilities are recorded in hiftory. A full view of cotemporary authors, and of that fucceffion of great men, which is of fuch importance both in civil and literary hiftory, is here placed before us. The charts are executed with neatnefs and accuracy on the part of the engraver, as well as of the author, and will be found of great ufe to every one interested in the hiftory of paft ages.

We have next a chronological table of remarkable events and occurrences in ancient and modern hiftory, from the crea tion of the world to the year 1783. The Appendix contains a great variety of tables neceffary for the illuftration of feveral parts of the fyftem. These tables are scattered through a number of books in the different fciences, and not eafily to be found. They are now brought together, and arranged in the moft convenient order.

The first of these is the Chronicle of Paros, originally engraved on those marbles which are now to be feen at Oxford. It was compofed when Diognetus was Archon of Athens, 264 years before Chrift. Among the most important of the marbles that follow, are those of the Olympiads; a lift of the Theban kings, from Eratofthenes; of the Chaldean, Perfian, and Egyptiankings, from Ptolemy; of the months of various nations, both ancient and modern, compared with the Roman month; - a table of epochs-limits of folar eclipfes ;--a table fhewing the different dates given to the creation, of which there are no less than 88. The two extremes are, that of Alphonfo king of Caftile, who carries back that event 6984 years before the Chriftian æra, and that of a Rabbi Lypman, who brings it down to 3616 before the fame æra.-This is followed by a very copious biographical index, digefted in alphabetical order, containing REV. April, 1774. U

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not only the names in the charts, but many others that could not find a place there; with a short character fubjoined to each.

Such is the skeleton of the elaborate work before us. It is a thefaurus of chronological knowledge, much more ample and judicious than anv that has yet appeared; uniting the advantages of many different fyftems, and felecting from them what is most valuable, while, at the fame time, it combines them with fuch skill, as to merit the praife of originality. Dr. Playfair avoids the faults into which a chronologer is moft apt to fall; for he is various without being perplexed, extenfive without being fuperficial, and accurate without being tedious. In a work where order and arrangement are objects of the first importance, it is of confequence to remark, that the printer and engraver are entitled to a very confiderable degree of praise; and that we do not remember to have feen a book of equal fize and elegance that could be purchased for so small a fum.

We shall conclude with obferving, that it is extremely difficult, if not abfolutely impoffible, to avoid inaccuracies and errors, in a work where fuch a multiplicity of dates is to be afcertained and adjufted. Accordingly, we have difcovered feveral errors in our Author's biographical index, which we are glad to be informed he has corrected, in an additional half fheet, that will foon be publifhed.

It is proper likewise to observe, that if what he now offers to the Public meets with approbation, he intends to publish fome chronological differtations, containing his reafons for rejecting fome opinions which have been long established, and adopting others not generally received. Thefe differtations will be accompanied with a felect number of maps, relating to ancient and modern hiftory, fome of which are to be conftructed on a new plan; together with the hiftory of Geography, from its origin to its latest improvements.

ART. VII. An Effay on Electricity, in which the Theory and Practice of that ufeful Science are illustrated by a Variety of Experiments. To which is added, An Essay on Magnetism. By George Adams, Mathematical Inftrument Maker to his Majefty. 8vo. 5 s. Boards Sold by the Author, No. 60. Fleet-ftreet. 1784.

W

HENEVER an author appears to be poffeffed of candour and modefty, we are always tempted to allow his own words to ftamp the character of his performance. Thus, in the present inftance, Mr. Adams fays in his preface;

It has been my endeavour, in the following Effay, to collect and arrange, in a methodical and concife manner, the effential parts of electricity; by thefe means to render its application eafy, pleafant,

and obvious to the young practitioner. Though the nature and confined limits of my plan did not admit of much variety of obfervation, or a formal enumeration of every particular, yet few things, I hope, of use and importance, have been omitted.'

We fee, hence, that Mr. A. does not pretend to have added to the facts already known in electricity; but to put into the hands of beginners a practical introduction, which, with the help of the apparatus he prepares, may enable them to repeat most of the experiments hitherto made, and to arrive at all we know of the principles of this important branch of philofophy.

The experiments here defcribed are no lefs then 226 in number. They are diftributed under the following heads: 1. Of Electricity in general. 2. Of the Electrical Machine. 3. and 4. Of Electrical Attraction and Repulfion. 5. Of the Electric Spark. 6. Of Electrified Points. 7. Of the Leyden Phial. 8. Of the Battery. 9. Of Conductors for Buildings, with a brief ftatement of the Wilfonian Controversy. 10. Of a charged Plate of Air. II. Of the Electrophorus, from Volta. 12. Of Atmospherical Electricity, from Father Beccaria. 13. Of the Diffufion and Subdivifion of Fluids by Electricity, from Nollet. 14. Of the Electric Light in Vacuo. 15. Of Medical Electricity, chiefly, we apprehend, from Cavallo. 16. Miscellaneous Experiments and Obfervations.

And,

Although we have intimated, that the Author does not profels to give any new discoveries in this publication, yet as the paffage in which he explains the excitation of an electrical machine contains fome hints which we do not recollect to have met with elsewhere, we fhall not fcruple to infert it here, for the information of fuch of our electrical readers as may not have opportunities of perufing the work.

In order to find out an effectual mode of exciting powerfully an electrical machine, it is neceffary to frame an idea of the mechanifm by which the cylinder extracts the electric fluid from the cushion, and those bodies which are connected with it: I have therefore fubjoined thofe conjectures on which I have worked, and by which I have been able to excite, in the most powerful manner, thofe machines which have paffed through my hands.

It appears to me, that the refillance of the air is leffened, or a kind of vacuum is produced, where the cushion is in close contact with the cylinder. The electric matter, agreeable to the law obferved by all other elaftic fluids, is preffed towards that part where it finds leaft refiftance: the fame inftant, therefore, that the cylinder is feparated from the cufhion, the fire iffues forth in abundance.

The more perfect the continuity is made, and the quicker the folution of it, the greater is the quantity which will proceed from the cushion. But as the fluid in this fituation will enter with avidity every conducting fubftance that is near it, if any amalgama lies above that part of the cushion which is in contact with the cylinder, it

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will