Jeffened; he is fenfible of the great difficulty of removing the moft important obftacle to diftinct and perfect vifion through microscopes, viz. the aberration of the rays, occafioned by their different refrangibility. The error hence arifing has been happily corrected in telescopes by Mr. Dollond's valuable discovery of achromatic glaffes; but how far the invention of that ingenious optician is applicable to microscopes has not yet been afcertained. Mr. Adams thinks there is some reason to suppose, that this invention cannot be fuccefsfully applied to microfcopes. We do not contradict the fuppofition, yet how can we pretend to know Quid craftina volveret atas? And let it be remembered, that Mr. Dollond removed an obftacle which withftood Sir Ifaac Newton's ingenuity, and reiterated labours.

The magnifying powers of microscopes come next under our Author's confideration; for the determining of which, he prefers mechanical methods to calculations, and defcribes a wellconftructed micrometer, by which not only the magnifying power of the microscope may be obtained, but the fize of objects measured.

The next chapter deferibes compound microscopes, of various conftructions. The preference is certainly due to Mr. Adams's lucernal microfcope, and we wish that, for the entertainment of our Readers, we could give an adequate description of this excellent inftrument, without the plates; as this, however, cannot be done, we content ourselves with reciting its fuperior advantages over others. It is adapted either for opaque or transparent objects; and the former are illuminated fo as to preferve in the image, a peculiar brilliancy of colour, and, what is of much more confequence, the concave and convex parts of the object retain their proper form. Another very confiderable advantage in this inftrument, is, that the objects need no previous preparation, by which their texture, and the configuration of their more tender parts, are often hurt. The ease with which the outlines of the object may be drawn is also a circumstance almoft peculiar to this inftrument, which throws the image of an opaque obje& on a grey glass.

After the lucernal microfcope, Mr. Adams defcribes Cuffe's double microscope; two others, on the fame principles, improved by the Author; Culpepper's microscope; an improved folar microscope for opaque and tranfparent objects; another for transparent objects only; Wilfon's fingle microfcope, another improved, another for opaque objects; Ellis's aquatic, Lyonet's anatomical, and Withering's botanical microscopes. The chapter clofes with the defcription of a portable inftrument, which is at once both a microfcope and telescope.

The fourth chapter contains fome general inftructions for afing microfcopes, and preparing the objects. Thefe directions

are

are compiled from the best writers on the fubject, and interfperfed with many original remarks, especially on finding, feeding, and preferving polypes, and procuring the animalcula infuforia.

The fifth chapter contains the elements of entomology, chiefly compiled from Fabricius' Philofophia entomologica, Reaumur, De Geer, and other approved writers. Mr. Adams minutely defribes the metamorphofis of infects in general, and illustrates his affertions with many interefting particulars. The economy of feveral tribes of infects is alfo largely treated. In a word, the naturalift will here meet with a pleafing variety of curious facts, which are difperfed through many voluminous works. We fhould have been happy to have found any thing very new in this valuable collection, which might have been felected for the entertainment of our Readers. Novelty, however, or rather the defcribing new difcoveries, feems not to have been fo much the defign of the Author, as the collecting and bringing into a proper compafs, the obfervations and difcoveries that have been made before him. In the execution of this office, he hath ac quitted himself well; and the perufal of the book will convince the reader that Mr, Adams's labours have been great, and that his acquaintance with all the beft writers on the fubject is extenfive.

In the next chapter, Mr. Adams gives the anatomy of a caterpillar, from Mr. Lyonet, and of the parts of several other infects, viz. the Lepas Anatifera, the fting of a bee, and the wings and eyes of various infects; and he defcribes many other microscopic objects.

The feventh chapter contains the (we had almoft said complete) natural hiftory of the Hydra, or fresh-water polype. The various properties and fingular appearances of the different fpecies of Hydra are brought into one view, and the progrefs of the dif coveries made by Trembley, Baker, Bonnet, Reaumur, Buffon, and Folkes, are traced with caution and accuracy; and the facts afferted by these gentlemen, to whofe affiduity and observations we are indebted for the knowledge of the nature and economy of this genus of animals, are confirmed by accumulated evidence. Mr. Adams defcribes feven fpecies of the HYDRA, viz. viridis, fufca, grifea, pallens, hydatula, ftenterea, and facialis; nine of the VORTICELLA, viz. anaftatica, pyraria, cratagaria, opercularia, umbellaria, berberina, digitalis, convallaria, and urceolaris; and ́ the Tubularia campanulata.

The natural hiftory of the animalcula infuforia forms the subject of the next chapter. By animalculum Mr. Adams undertands all thofe animals which are altogether invisible to the naked eye. We here enter the confines of a new world, the mundus invifibilis, inhabited by numerous fpecies of animals,

R 3

which

which from their minuteness muft have remained unknown, without the aid of microfcopes. Who can fay how many of thefe invifibles there may be? They are difcernable of all fizes, from those which are barely feen with the naked eye, to thofe which refift the action of the microfcope, and appear like moving points, even when viewed with inftruments of the greateft magnifying power. May not others exift as fmall in comparison to thefe, as these are to elephants?

After much reasoning on the subject, Mr. Adams examines the opinions of Buffon, Needham, and Munkhaufen; and refutes their hypothefes with ingenuity. This part of the work appears unneceffary, fince the fuppofitions of these gentlemen were difcredited by Bonnet, De Sauffure, Baker, Wrifberg, Spalanzani, Haller, and many others, and efpecially by Ellis, who, under the direction and at the request of Linné, made a long feries of obfervations on the infution of mushrooms; and the facts thence refulting were a full refutation of Needham's, Munkhaufen's, and Buffon's organic particles.

Mr. Adams proceeds to defcribe the individuals of the mundus invifibilis; he follows the arrangement of Muller, and gives the difcriminating characters which that laborious naturalift has adopted; abridging, enlarging, or altering the defcriptions, fo as to render them in fome inftances more exact, in others lefs tedious, and on the whole more interefting to the reader. The animals here described are in number 379. Moft of the defcriptions are accompanied with drawings, exhibiting the animal in different pofitions and circumftances. Mr. Adams gives a more particular account of thofe animals that most frequently occur, than of those which are uncommon; in doing which he most certainly affifts the tyro in this branch of natural hiftory: but the adept in fcience would, doubtlefs, have been more gratified had the Author enlarged his defcriptions of the rare animals, and given ample directions where they were to be procured. The eels in pafte and blighted corn, have been obferved by various authors: they are, undoubtedly, curious animals, and have given rife to many fpeculations and theories among naturalifts. Mr. Adams has therefore justly extended his account of them. One of the moft remarkable properties of this animal is, in the Author's opinion, its revivification, or the faculty of receiving again the powers of life, after having loft them for a confiderable time, even after having been dried for feveral years. This property, we believe, is not fingular, being common to other species of worms;-perhaps the Hydra may poffefs the fame faculty. We know not that any experiments have been made to ascertain the fact in this wonderful genus of animals; it furely merits the attention of the obferver. It may be objected, that observations of this kind do not apparently tend to any important purpote.

We

We may not, at prefent, perhaps, know to what uses they may be applied; but as the advancement of the ftudy of nature depends wholly on phenomena, an accumulation of facts must neceffarily form the bafis of every true system.

The ninth chapter is on the organization, and conftruction of timber. This fubject opens to the naturalift an extenfive field of obfervation. Malphigi, Grew, Duhamel, Hill, Bonnet, and De Sauffure, have been Mr. Adams's predeceffors in this branch of natural history. The rude ftate of the inftruments used by fome of these gentlemen, in their examination of objects, renders a repetition of their obfervations abfolutely neceffary. It muft be acknowledged that they have made great progrefs, but much remains to be done, before the theory of vegetation can be firmly established. Though Mr. Adams has followed Sir John Hill's fyftem; yet he examines the opinions of Grew, Duhamel, and other writers. We do not find that he hath mentioned the Linnæan hypothefis of the prolepfis plantarum. Microscopic obfervations are much wanted to fupport that ingenious fuppofition. It certainly explains the phenomena of vegetation better than any other hypothefis, and, on that account, demands the serious attention of the minute obferver.

The laft chapter is on the cryftallization of falts, as feen by the microscope, and the manner of preparing different objects.

We have endeavoured to give our Readers the contents of this valuable work, which we doubt not will be read with pleafure by the naturalift, and with inftruction by thofe who are lefs acquainted with the fubject. Mr. Adams has not, it is true, given a complete fyftem of optics, but he has given an admirable practical treatife on the microfcope, and microfcopic objects. The plates illuftrating the feveral parts of the apparatus, convey just ideas of the inftruments; and the numerous figures of the objects, which are accurate reprefentations of nature, fully fhew the great pains bestowed by the Author in examining the minute parts of the creation. It is impoffible to view thefe beautiful objects, without contemplating, and reflecting with aftonishment, on the power and wifdom of the Creator; and fuch reflections Mr. Adams frequently introduces, with great propriety, and with very natural effect.

In a word, this publication will not only be acceptable, but ufeful to all who amufe themselves with microfcopic obfervations, as well as to those who wish to increase that knowledge of the invifible world, which the powers of human investigation have already attained.

ART. XII. Memoirs of Henry Mafers de la Tude, during a Confine, ment of thirty-five Years in the State-prifons of France. Of the Means he used to efcape from the Battille, and twice from the Dungeon of Vincennes, with the Confequences of thofe Events, Written by himself. 12mo. 25. fewed. Robson, &c. 1787.

M.

De la Tude informs us, that he was committed to the Baftille, in the year 1749, at the inftance of the Marchionefs de Pompadour, whom he had inconfiderately, and with no ill-meaning, offended. The manner in which he effected his escape from the higheft of its towers, and which is detailed in the prefent volume, is fuch as greatly ftaggers our belief: but if the narrative be indeed authentic (as we imagine it is, notwithftanding the great improbability of many of its circumstances), his fufferings may well have impelled him, as they did, to the moft hazardous and daring attempts. As he was imprifoned by virtue of lettres de cachet, and as thefe inftruments of arbitrary power are, with juft abhorrence, reprobated by our countrymen, we will extract the Editor's (it is not the Author's) argument in favour of them: according to which, they have their foundation in reason, and a love of justice; and it is only the abuse of them which we ought to condemn*:

In a conftitution like that of France, lettres de cachet may, and do, ferve to prevent the ferious confequences with which an infraction of fome of the penal laws are attended. Whole families are dithonoured, for feveral generations, by the profligacy of any member of them, when conviction and legal punishment ftops his wicked career, A Frenchman, guilty of a high crime or misdemeanor, and punished for it, deftroys his family, its collateral branches, even in honour and profeffion, and renders his near relations incapable of holding any employ under the Crown: fo that his father, brothers, uncles, &c. fuffer more than himself, and remain living monuments of the infamy of an unprincipled wretch, who has been fnatched from among them by the unerring hand of justice,

Were it not from a natural effort to prevent the innocent from fuffering with the guilty, lettres de cachet would feldom be made use of. It is publicly known, that the reigning monarch is a great lover of justice; and that, fenfible of the unlimited power with which he is invested, he is ever on his guard against the infinuations of men immediately about his perfon, left, by an imprudent attention to their requests, he should be furprised into acts of authority, which, upon mature deliberation, might appear to have been unneceffary.

A very refpectable writer informs us, that the Bastille is by no means fo terrible at the prefent day as in former times; and that the number of prifoners has not, of late years, amounted, at any one time, to more than nine or ten perfons. The expences neceffarily attending this State-prifon are, however, fo very confiderable (not lefs, according to fome accounts, than twenty-five thousand pounds fterling per annum), that it will probably be foon annihilated."

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