One of these is termed the Magical Picture.'-A piece of flat glafs is to be placed over another of the fame fize, from which it is kept feparated about a twentieth part of an inch, by four pieces of paper pafted on the four corners. These glaffes are joined together at the edges by a luting, composed of Macked lime and the white of an egg, except in one place, where a small aperture is left. Through this opening is to be introduced a melted mixture of fine hog's lard and white wax, in fuch proportions as that it will barely congeal, in a room in which there is no fire. A picture or coloured print is then to be pafted with its face to one of the glaffes, and the whole is to be put into a frame. On being brought out of a cold room, the print will be invifible, or the space within the frame will appear blank. On hanging it up however near the fire, the mixture will foon become perfectly transparent; and our magician may then be enabled to exhibit a picture feemingly produced by his art, and which will appear as if there were only a fingle glass before it.

Some amusing tricks and deceptions are founded on the qualities of the various fympathetic inks, which are here copiously, described. One of the most ingenious of these deceptions (the idea of which was, we believe, first suggested by M. Hellot, in his memoirs on this fubject,) is the feventy-third recreation in the fourth volume. It is intitled, Winter changed into Spring, and may be thus performed.

A fympathetic ink is made by diffolving zaffre in aqua regia, and diluting the folution with water. Forms, or characters, drawn or traced with this fluid, will not be vifible unless they are exposed to the warmth of the fun's rays, or are brought near a fire, where they will appear of a lively green colour. A print is taken, or a drawing made, that represents winter, in which the ground appears naked and dreary, and the trees without leaves. The intended foliage and grafs is to be drawn with the fympathetic ink, in the proper places, and will remain invifible. On hanging the print however in the fun's rays, or near a fire, a new creation will appear; for the scene, which before represented Winter, will now exhibit the beauties of Spring, by the appearance of the luxuriant foliage that had been drawn with the invifible ink. On placing the drawing in the cold, Winter will reaffume its feat, and it will be again fucceeded by Spring, on replacing the print in its former warm fituation. Thefe changes will happen repeatedly, toties quoties, unless the print fhould be expofed to too great a degree of heat; in which cafe it will ever afterwards exhibit the appearance of Autumn.

In fome of the recreations the Author is not always fufficiently accurate or explicit, and indeed in fome cafes does not

feem

seem to be well acquainted with the subjects of them: fo that a person who follows the directions here given, may frequently be disappointed, or be led into error, or into unneceffary trouble or expence, by attempting to perform them. We fhall exemplify the justice of this remark by two or three inftances only, taken from the fourth volume.

In recreation 39th, which is intitled, The fulminating Gold, the Author directs, that one part of the filings of pure gold fhould be diffolved in three parts of aqua regia; and that a fufficient quantity of spirit of fal ammoniac, or oil of tartar,' should be added, drop by drop, till all the gold be precipitated in the form of a powder, which is to be cautiously dried. If a grain of this powder,' he adds, 'be put in a copper spoon, over the flame of a candle, as foon as it is well heated, it will go off, with a report like that of a piftol. If the fpoon be not fufficiently ftrong, the matter will run through it, and make an explosion underneath, with great violence.'

As the Author is not writing to chemists, but to the curious in general, or to the philofophical dilettanti, he ought to have described this recreation or process in such a manner, as that it might invariably fucceed with every one who was disposed to amufe himself with it: but, as it is here delivered, it may frequently fail with those who try it. He ought to have recollected that aqua regia is fometimes prepared by adding sea salt, or its fpirit, to the nitrous acid; as well as by diftilling the latter from fal ammoniac. Now it is certain that unless fal ammoniac has been employed in the preparation of the aqua regia, or unless the gold diffolved in the other kinds of aqua regia is precipitated by a volatile alcali;-in fhort, unless there be a volatile alcali in fome of the materials concerned in the experiment, the expected aurum fulminans will not fulminate. Author ought therefore either to have specified that the aqua regia fhould be that prepared with fal ammoniac, (in which cafe, it is indifferent whether the precipitation be made with spirit of fal ammoniac, or oil of tartar) or, as that circumstance might be unknown to the experimenter, he ought, to fecure him from disappointment, to have directed him to precipitate the gold with spirit of fal ammoniac only. The phænomenon indeed wholly depends on a nitrous ammoniacal salt formed in the process, and intimately combined with the particles of the precipitated gold.

The

Similar and repeated disappointments, attended with vexation and expence, muft generally be the confequence of attempting to perform another curious chemical experiment, according to the Author's directions, given in his 47th recreation; the title of which is, To produce fire by the mixture of two cold liquors. Copying probably fome former copyift, as is customary with

mere

mere compilers, who do not avail themselves of late difcoveries and improvements, the Author has delivered the process for producing this curious phenomenon, nearly in the fame ftate of imperfection in which it was firft propofed, in the middle of the laft century, by the difcoverers, Becker and Borrichius.

After a brief, but unneceflary defcription of the method of making Glauber's strong spirit of nitre, the Author adds that if to a drachm of diftilled oil of cloves, faffafras, turpentine, or caraways, contained in a glass veffel, there be added an equal quantity, or half as much more, of the above fpirit, though both the bodies are perfectly cold before the mixture, a violent flame will inftantly arife, and entirely deftroy them, &c.'

The procefs, as here delivered, has almoft conftantly failed, even with many of the greateft chemifts in the laft and prefent century; feveral of whom have applied themfelves to the improving it, and have fucceffively discovered the circumstances that may contribute to the fuccefs of it; particularly Hoffman and Geoffroy, the laft of whom rendered the fuccefs much lefs problematical by adding fome concentrated oil of vitriol to the nitrous acid. Ás this is one of the most curious phenomena in chemistry, we shall supply the Author's deficiencies by fubjoin. ing a few obfervations on this ftriking experiment.

In a memoir on this fubject, M. Rouelle has not only infured the fuccefs of the operation with refpect to all the effential oils, but likewife to the lefs coftly expreffed oils of linfeed, nuts, &c. by ufing the concentrated nitrous acid alone; and has fhewn how even the common oils, of a lefs inflammable nature, fuch as thofe of olives, almonds, &c. may be kindled, The following hints, collected from M. Rouelle's memoir, may not be unacceptable to the curious.

To an ounce of any effential oil, or of the expreffed drying oils, fuch as those of linfeed, &c. half or two thirds of an ounce of the ftrongeft fpirit of nitre is to be added; the veffel which contains it being held at arm's length, tied to the end of a flick ; to prevent accidents, which fometimes attend the explosion. The matter becomes black and thick. If flame is not produced within a few feconds, about half an ounce more of the nitrous acid is to be poured on to that part of the fermenting mafs which appears thickest and drieft; and then it never fails to burst into flame.-With respect to the other clafs of oils, as thofe of olives, &c. it is neceffary firft to add to them equal quantities of the concentrated vitriolic and nitrous acids; and when the fermentation is at its height, a little of the pure nitrous acid, poured on to the thickest part of the mixture, feldom fails to fet it on fire.

See Mem. de l'Acad. Roy. de Paris, Année 1747, p. 49.

The

The 14th recreation of this volume may be attempted for ever without fuccefs, unless by accident, with respect to one of the phenomena, if the operator merely follows the directions given by the Author, It is called The mercurial Shower, which is produced by cementing a piece of wood pretty low within the neck or top of the receiver of an air-pump, and pouring fome mercury over it. On exhaufting the receiver, the mercury will be forced, fays the Author, through the pores of the wood in form of a beautiful shower; which, if the receiver be clear, and the weather be dry, will appear luminous in a dark chamber.'-But mercury has no phofphorine quality, either in the common or in rarefied air. In the infancy of electricity indeed, Hawkfbee produced a luminous fhower, on trying an experiment not very different from this, except in this effential circumftance, that the mercury dashed against the top of a glass vessel placed within the receiver, and produced light, which has been long known to be electrical. Without fuch a friction of the mercury against glass, no light will appear; nor is any likely to be produced, except by mere chance, in performing the prefent

recreation.

Notwithstanding these and fome other inaccuracies, over, fights, or defects, and that the difficiles nuge conftitute rather too large a part of this work; the articles contained in it may afford an innocent amufement to thofe who are not well ac quainted with the many curious phenomena that are prefented in philofophical experiments. The moft frivolous in the collection may have their use, if they incite the reader to the ferious ftudy of thofe ufeful or entertaining branches of knowledge to which they relate. B-Y.

ART. V. The Hiftory and Antiquities of the County of Dorfet: Compiled from the best and most ancient Hiftorians, Inquifitiones poft mortem, and other valuable Records and MSS. in the public Offices and Libraries, and in private Hands. With a Copy of Domesday Book and the Inquifitio Gbeldi for the County: Interspersed with fome remarkable Particulars of Natural History; and adorned with a correct Map of the County, and Views of Antiquities, Seats of the Nobility, Gentry, &c. By John Hutchins, M. A Rector of the Holy Trinity in Warham, and of Swyre, in the County of Dorfet. Fol. z Vols. 31. 35. Bowyer and Nichols. 1774.

MR

R. HUTCHINS's most elaborate performance muft be confidered as a very valuable addition to the various diftinct county-histories of which the public was before in poffeffion. It appears to be equal to moft of them in accuracy, and it is fuperior to them all in the beauty of the impreffion ;more especially, in the number and elegance of the ornamental engravings.

In ftating his general motives for attempting the history of his own county, our Author expatiates on the peculiar claims of Dorfetfhire to the honours of hiftorical celebrity. It is a county, he observes, which, for the advantages of its fituation, fertility of its foil, rare productions, the many remains of antiquity with which it abounds, the many remarkable actions of which it has been the scene, and the many perfons eminent in various arts and fciences to which it has given birth, well deferves an hiftorian more equal to its merits, and cannot fail to answer all the labour and pains of the most diligent enquirer !'

In 1739, Mr. Hutchins difperfed circular letters, announcing his plan, and foliciting affiftance; which, in the course of a number of years, he obtained in abundance: as appears from the many grateful acknowledgments which he has inferted int his preface. It seems, however, that, notwithstanding the numerous and important communications of his learned friends, and other helps, his work would ftill have been left very imperfect, had not an hand fome fubfcription been procured for it, in 1761, among the gentlemen of the county; which enabled the Author to search the Bodleian library, the Afhmolean mufeum, and the libraries of private colleges in Oxford, the British Museum, the Tower, Rolls Chapel, Augmentation Office, and other public repofitories of records and manufcripts in London.

6

• Thus furnished with materials,' fays he, much care was to be taken in the choice of them, that on the one hand, nothing worthy to be preferved might be omitted, and on the other, that nothing too minute and trifling might be inferted. This laft error,' adds the Author, [confcious that many thingswhich will feem disgustingly trivial to moft readers, must neceffarily appear in a compilement of this kind,]feemed the moft pardonable; for what fome might think fuperfluous, might appear to others worthy of attention; and on the whole, if in fearching into fuch an heap of ruins, fome duft be collected with the gold, like ruft adhering to coins, though it adds nothing to their intrinfic value, yet it is in itself a proof of their antiquity: and for all imperfections of this nature, I hope to find an easy cenfure.'

With respect to the ornaments of style and diction, they will not be much fought for in works of this fort. If the Author's manner of writing be not abfolutely heavy, dry, and tedious, we ought not to expect much more: and this praise, at least, is due to Mr. Hutchins. He fpeaks of his own merit, in this respect, in very modest terms. Whatever,' fays he, " is wanting in ornament, I have endeavoured to fupply by accuracy, perfpicuity, and method; and the whole is interfperfed with

historical