pafs; who owneth no particular home, and who is of a steady mind. They who feek this amrěětă of religion even as I have faid, and ferve me faithfully before all others, are, moreover, my dearest friends.'

The three next Lectures contain an explanation of Eastern terms, of which we can give no analyfis.-The fixteenth is on good and evil deftinies ;-the feventeeth on Faith divided into three Species; and the laft, on forfaking the Fruits of Action for obtaining eternal Salvation.

We have given the most comprehenfive account in our power of this very curious work; but, while we own that it must be neceffarily inadequate, we hope it will excite the curiosity of our readers to perufe a work, fuppofed to be written near eight hundred years before the time of Mofes.

A Differtation on Elective Attractions. By Torbern Bergmann. Tranflated from the Latin. 8vo. 6s. in Boards. Murray. Perhaps we may, without incurring the charge of rafhness

or precipitation, trace the rapid progrefs of chemistry from the period in which tables of elective attractions were first formed. From the time of Geoffroy, our labours have been more pointed and accurate, our conclufions more clear and decifive, and chemical knowledge, in general, more improved than in the long feries of ages which preceded. Some of thefe additions, to our knowlege, may undoubtedly be attributed to the spirited investigations of an enlightened age, to the liberal mode in which enquiries are now carried on, and to the number of labourers in the field of fcience; but it will be at once obvious that to ascertain what has been done, and where our experience is deficient, is the firt method of directing enquiries to the best purpose, and of preventing others from wafting their time on what is already known. M. Geoffroy, therefore, who published the firft Table of Affinities in 1718, has gained by it the highest reputation, though the table itself was fhort, imperfect, and indecifive. It was, however, the firft attempt, and the fame which he acquired has been in a great degree fupported by his other works. In the age of Geoffroy, foon after his firft publication, an obfcure chemist in Germany, M. Groffe, improved and added to his lift. He read, he studied, and made experiments in filence and obfcurity at his window he delighted to puzzle the paffengers; but never would explain any thing till he had completely astonished them. This table was privately copied, and never published till 1748. We have given these particulars to rescue his name from oblivion, and to inform the world of the peculiarities of its inftructor, He introduced a geometrical method of argu

ingi

ing; for instance, nitrated mercury, fea-falt, and vitriol, being given, what will be the refult of diftilling them together? This method exercised his pupils in the use of his table, but has introduced too much reasoning in a science which chiefly refts on experiment. Soon after this time, a flight attempt in the fame way was published in the early editions of Quincy's Difpenfatory.

In the year 1750, Mr. Gellert, a Saxon chemift, published a table with confiderable additions; but he entirely changed the order of the fubftances; for that which had the least relation to the body at the head, ftood in the first rank. His work was tranflated into French, in 1758; and Mr. Spielman adopted his table, in his Inftitutes of Chemistry, published in 1763. There are many errors in it, particularly respecting the effect of heat on the earthy bodies. It contained twenty-eight columns.

In 1736, M. Rüdiger published, at Leipfic, a Table of Af finities, in fifteen columns; to which were added, ten columns of fubftances which would not unite without preparation. This was a very useful addition: the explanations are in German; but this work is not valuable, on account of the irregularity of the order, and the few fubftances inferted in each column.

Another Table was published by M. Limbourg, in 1758. It is very full; but erroneous and imperfect. In 1763, that part of the famous Encyclopædia which relates to chemistry appeared, and in it a new Table, which has never been attributed to any author. It is chiefly compofed from those of Geoffroy, and the almoft forgotten Groffe, and is full of imperfections as well as contradictions. The new edition now publishing was, therefore, much wanted. Soon after this time, for our history has led us fo far, that we must haften to a conclufion, Dr. Black, in his clafs, gave an improvement of Geoffroy. Many new columns were added, and different fubftances fubjoined to the old ones, with more discriminating exactness. It was, at that period, the most perfect table that had appeared. In 1769, M. Machy read, at the Royal Academy, an explanation of his new table, which poffeffes great merit: and, in 1775, the Differtation of Bergmann, which has occafioned this detail, was published in the new volume of the Upfal Tranfactions.-Let us finish our history, in the words of the very intelligent tranflator.

Since the above, befides many alterations which totally change the difpofition of it, not lefs than nine new columns have been added, which, if all the rectangles were filled up, make 9 x 50450 new rectangles. I have no doubt but that

an

an equal or a greater number of additions will hereafter be made in an equal number of years. Even fince the publication of the third volume of the Opufcula, in 1783, two, or perhaps three fubftances have been difcovered which will claim a place on the Table of Elective Attractions; these are what Mr. Scheele confiders, as the acid inherent in tungtein, or lapis ponderofus, the metal which Meffrs. Luyart obtained from tungftein; for wolfram only differs from it in being combined with iron and manganese, and the acid of the filk-worm, and fome other infects, defcribed, by M. Chauffier, in the Dijon Memoires for 1783."

We have inveftigated this hiftory with fome attention, because we think it of great confequence. Since the first Effay of M. Geoffroy, though many have been the attempts to improve his Table, the fuccefs has not been proportional. Befides, the number of candidates who have contended with him for fame, has not been equal to thofe authors who have tranfcribed his arrangement, with little addition. Each of thefe have, till within these ten or fifteen years, joined in his praifes. About that time fo many exceptions feemed to occur to every attempt of this kind, that the best chemifts began to relax in their efforts, defpairing of bringing it to perfection. In fact, they employed fubftances as fimple bodies, which were really compounds; and they varied their experiments without being aware of, or allowing for, the variety. Confufion confequently fucceeded to order, and each general rule was clogged with exceptions fo numerous, that it loft its ufe. The discovery of the aerial acid began to lead chemists into a clearer light; and, by following this clue, Bergmann, in the work before us, has elucidated many difficulties, and reconciled many apparent contradictions.

Excefs of heat is one caufe of the feeeming exceptions; and irregularities arife, as we have hinted, from double attraction. We fhall infert a fhort fpecimen of our author's reafoning on this fubject.

Chemifts, in determining the fingle elective attractions, are often deceived by double attractions. The phofphoric acid, as I fhall hereafter fhew, attracts lime more powerfully than fixed alkali; yet the contrary is afferted, fince aerated alkali, by means of a double affinity, precipitates phofphorated lime. Even cauftic fixed alkali, which feems a ftronger proof, caufes a precipitation nevertheless, if the fuperior attraction is deduced from this alone, the conclufion will be erroneous; for the alkali only takes away the excefs of acid which is requifite for folution, and hence the phofphorated lime falls to the bottom. The difference between the action of alkalis and abforb ent-earths, when faturated with aerial acid, and when deftitute

of

of it, has been explained in my effay on that acid, and may, therefore, be omitted here. It may now, in general, be obferved, that alkaline and earthy fubftances are to be considered as double, and by no means as fimple falts, except in their cauftic ftate, and then I call them pure.

The precipitation of metals, diffolved in acids, by other metals, is never the effect of fingle attraction; for during the folution, a quantity of phlogiston is extricated, as I have clearly, I hope, fhewn elsewhere. Since, therefore, metallic folutions are of fuch a nature, that they cannot reftore what they hold diffolved to its metallic fplendour without the acceffion of a new portion of phlogifton, it is felf-evident, as well as conformable to experiment, that this cannot be effected by the addition of calces. If, therefore, echre be put into a solution of vitriol of copper, no copper will be precipitated; but iron added to the folution is foon obferved to be covered with a cupreous pellicle; for it yields part of its phlogifton, which is neceffary to the reduction of the copper, and by this means becomes itself foluble without the emiffion of any inflammable air. Silver diffolved in the nitrous acid, is in like manner calcined; as appears from the red vapour, phlogistic fmell, and various other evident figns, and therefore cannot be precipitated by the calx, though it may by regulus of copper. The fame obfervation is applicable to gold and the other metals; for in whatever way they be feparated, provided they can acquire no phlogiston, they appear calcined, and really are fo: the only difference confifts in this, that they are unequally dephlogisticated, and that the noble metals can recover their lofs by fufion alone in ignited veffels, whereas the ignoble ones require an addition of phlogiston.'

Exceptions which have been made, are also fometimes owing to a fucceffive change of fubftances; as, for inftance, the nitrous acid is phlogisticated by adding marine acid, and then adheres fo loosely to an alkali as to be diflodged by any acid., Nitre, kept fome time ignited, in the fame way may be separated even by vinegar; but the order in which a compound body is arranged, ought not to form an exception to the affinity of the body, when fimple. When a fubitance feparated is foluble in the menftruum, or when the folution is capable of diffolving the difunited body, we alfo fee an apparent, inftead of a real irregularity. The fame occurs when the fubftance, which we expect to fee separate, is capable of uniting to the new compound, or when a determinate excess of any of the ingredients is required to form the body, in a ftate fit for feparation; as of an acid in crude tartar, and of an alkali in borax. All these circumftances have perplexed the practical chemifts; and Bergmann's explanations, which cannot be expreffed in horter language than his own, are curious and inftructive.

Ha

He then examines each column in his Table, and explains. in general, the nature of the fubftance at the head, and the experiments on which the fubfequent order is founded. He tells us alfo, where they are arranged from analogy, and when from conjecture thefe difficulties must be removed by future experiments. Of a work fo mifcellaneous, we can give no regular analysis; and fhall extract only a fhort paffage, which contains information not generally known, viz. on the colouring matter of Pruffian blue.

:

I have long conjectured, not without reafon, that the tinging matter in Pruffian blue is of an acid nature, as it forms compounds of an intermediate kind with alkaline falts, as well as with earths and metals. Mr. Scheele has lately taught us how to feparate the acid in a pure ftate. Phlogifticated alkali, as it is commonly called, is a triple falt; containing the tinging acid, faturated partly with iron, and partly with alkali. This falt, boiled in a retort with weak vitriolic acid, emits the tinging acid in an inflammable aerial form, which may be abforbed by water placed in the receiver. And as at the fame time, fome vitriolic acid paffes into the receiver, the liquor fhould be again diftilled with a little chalk, till one-fourth fhall have paffed over; which is a folution of the prefent acid in water. The following procefs anfwers the fame end with lefs trouble: let fixteen parts of Pruffian blue be boiled in a concurbit, with eight of mercury, calcined by means of nitrous acid, and forty-eight of water, for a few minutes, with conftant agitation. The mixture becomes of a cineritious yellow; it should be put on the filter, and the refiduum elixated with boiling water. To the filtered liquor, let twelve parts of pure iron filings be added, and three of concentrated vitriolic acid. After a fhaking of fome minutes, the whole mass is turned black by the reduced mercury. After the fubfidence of the powder, the clear liquor is to be decanted into a retort, and one-fourth abstracted.'

A commentary on a table of elective attractions must contain an abstract of the whole fcience; and the abstract before us is not only full and comprehenfive, but clear and fatisfactory. New discoveries muft, however, have affected many parts of the work; and fome mistakes, the errors of humanity, may be occafionally obferved. Many of these are corrected by the tranflator, who, befides adding some valuable notes, has executed his task with great skill and judgment. He appears to be of opinion, that the late discoveries relative to the nature of water, by Mr. Cavendish and Mr. Watt, are fully established; but we ftill entertain fome doubts. If they are once exactly afcertained, we agree with him in thinking that they will have an extenfive influence over every branch of chemical know