In the 18th chapter, he confiders the nature of the external covering of the nerves, and of the fubordinate cords of which they confift; and he shows, that anatomifts have erred in fuppofing that they are covered by the pia mater only.

Ch. 19, contains remarks on the ftructure of the ganglia of the nerves. On this fubject Dr. Monro has difcovered that the nervous fibrils do not difappear in the ganglia, as former authors had imagined. Thefe fibrils, on the contrary, may be traced from their entrance into a ganglion through the whole substance of it, till they iffue out from the oppofite furface. In their tranfit, however, the fibrils form many new combinations, change their direction, and the whole of them, within the ganglion, are encrufted with a vascular matter, resembling the cortical fubftance of the brain. From this difcovery, the Author contends, that, in iffuing from a ganglion, the nerves receive an additional matter, and acquire a fresh energy. Hence he deduces the reason why ganglia are most numerous in those nerves which are allotted to organs of chief importance in the animal œconomy, and why thefe organs are most remarkable for the extent of their fympathy.

Chap. 20th, informs us of a curious difcovery which the Author has made, of fpheroidal bodies adhering to the brain and nerves of certain fifhes. These bodies must perform fome important, though unknown function, the discovery of which may throw light on the nature of the nervous energy.

In the 21ft chapter, fome principal nerves are defcribed, which have not been properly, or at all, traced by former anatomifts, namely, a nerve fpent on the ligaments of the wrist; nerves entering the teeth; the rife of the great fympathetic from the fifth pair; the rife and progrefs of the chorda tympani ; a plexus formed by the joining of the recurrent nerve with the fuperior laryngeal; the termination of the retina in the eye; and the courfe and very curious termination of the nerves in the organs of fmelling and hearing.

Ch. 22. Here the Author defcribes the appearance of nerves when viewed with the microfcope. The ultimate fibres of the nerves, when viewed by a microscope which magnifies the diameter of objects 146 times, have a ferpentine or convoluted appearance. The fame convolutions, upon examination, were equally confpicuous on the trunks of the nerves, on the muscles, on the bones, the ligaments, and even on the hair of the body. Similar convolutions are to be obferved, not only in the vegetable, but in the mineral kingdom. After defcribing these appearances, the Author, from various experiments and reafonings, concludes, that they are mere optical illufions, which may very readily mislead unwary obfervers. Ch. 238,

Ch. 23d, confiders the nature of the nervous energy; and endeavours to fhow, that the power poffeffd by the Torpedo and Gymnotus, of communicating an electrical fhock, is by no means a proof that the nerves convey an electrical fluid; and the Doctor alleges that there is no proof that any very fubtile fluid is conveyed by them with great velocity: on the contrary, he thinks, from certain experiments, that the energy of the nerves depends on a matter capable of being affected by fimple preffure.

After mentioning, in chap. 24, that the nerves are the inftruments by which animals feel, and are enabled to perform motion, he proceeds, in the next chapter, to examine a doctrine maintained by fome eminent authors, that the nourishment of animals is conveyed and applied to the different parts of the body by the nerves. But, from a variety of arguments, and from new, and, in our apprehenfion, decifive experiments, he concludes, that few points in phyfiology are clearer than, ift, That the arteries prepare and directly fecrete the nourishment in all animal organs; and, 2d, That the nerves neither contain nor convey the nourishment, but merely contribute indirectly to nutrition, by enabling the arteries to perform their proper functions.

The learned Author treats in chap. 26. of sensation; and attempts to prove, that, in all animals, there are two fpecies of feeling. The firft is accompanied with confcioufnefs; and the fecond produces no effect on our perceptions. This laft kind of feeling he compares to that which he fuppofes to be inherent in the vegetable kingdom.

In the 27th chapter, our Author endeavours to prove, that the muscular fibres are not formed by the nerves; and, therefore, that these fibres have been with much impropriety denominated the moving extremities of the nerves. He likewife fhews, that the muscles are organs fui generis; and that they are influenced only by the energy which the nerves convey. Notwithstanding the above conclufion, he demonftrates, by various experiments and obfervations, that the muscles do not, as Dr. Haller contended, poffefs a vis infita different from the vis nervea.

The laft chapter treats of the manner and causes of mufcular action. After enumerating the chief fpontaneous motions of animals, in that order in which they ought to be arranged, when an investigation of their caufes is intended, he concludes, that these causes cannot be accounted for, either from the connection of nerves, or from any known principles of mechanifm; but that they are directed by a wife Agent, intimately acquainted with animal ftructure, and with all the effects it is capable of pro❤ ducing,

For the purposes of phyfic, he remarks, it is perhaps fufficient that we know the ftimuli which excite the spontaneous motions, and the manner in which they are performed. But as philofophers have made feveral abortive attempts to explain the nature of the agent which produces thefe motions, our Author endeavours to fhew, that, unlefs the mind poffeffes innate knowledge, and power of which it has no confcioufnefs, the caufe of these actions must be referred to a higher fource. He therefore concludes, that the Power which created the univerfe, which gave life to animals, and motion to the heavenly bodies, continues to act upon and to maintain the whole, by the unremitting influence of a living principle, the nature of which our faculties are incapable of duly comprehending.

From the above analyfis our Readers will be enabled to form. some idea of the nature and objects of this performance. No part of anatomy merits fo much attention from philofophers as the ftructure and ufes of the brain and nerves. These organs are, not only the inftruments of motion, as well as of fenfation, but the medium in all refpects between mind and body. They are, of course, the fources through which all knowledge is derived. Senfible of the importance of the fubject, the learned and ingenious Author has, for many years, made it a principal object of investigation. By unwearied application, and well-directed experiments, he has difcovered many circumstances concerning the ftructure and functions of the brain and nerves, which are not to be found in the writings of any other anatomift: the Public are therefore much indebted to the Doctor for communicating to them the refults of his laborious and useful inquiries.

With regard to the execution of this work, the compofition is every where plain and fimple; and the defcriptions, though often minute, are always fo perfpicuous, and fo largely illuftrated by numerous tables, that they may be readily understood by those who have not bestowed much attention upon anatomical fubjects.

As to the merit of the plates them felves, we are afraid that an eye accustomed to the elegance of modern engraving, will not view them without fome degree of diffatisfaction. They are for the moft part coarfely executed: and though, affifted by the explanations, they may tolerably ferve the purpose of illuftration, they muft fail in giving that lively idea of the object, which the hand of a mafter is able to impart.

1

ĀRT,

ART. V. A Tour in Wales. Vol. II. Part ii. 4to. 14s. 6d. Boards. Payne and White. 1783.

HIS agreeable and inftructive Road-companion, has How agreeted his Welth Tour; the firft volume of which appeared in 1778, and had a place in our Review for January 1779. The Author's Journey to Snowdon was a diftinct publication; though it is confidered as a continuation of the Tour in Wales: an account of it was given in the Review for November 1781.

This concluding Volume of our ingenious Author's survey of his native country, comprehends the remainder of his defcription of Caernarvonshire, (begun in the volume relating to Snowdon) together with the ifle of Anglefey, the county of Montgomery, and part of Shropfhire, particularly Shrewsbury, the antient feat of the British princes.

Having, occafionally, given very ample extracts from Mr. P's. travels, and, perhaps, fufficient fpecimens of this Tour in particular, it may be thought, in fome measure, unneceffary to make any felection from the volume before us; but we cannot refift our inclination to entertain our readers with the following curious account of the vast copper mine in the ifle of Anglefey; which he fpeaks of as the moft confiderable work of the kind that was ever known: and we believe he is right:

The external aspect of the hill* is extremely rude, and rifes into enormous rocks of coarfe white quartz. The ore is lodged in a bafon, or hollow, and has on one fide a fmall lake, on whofe waters, distasteful as thofe of Avernus, no bird is known to alight. The whole afpect of this tract has, by the mineral operations, affumed a most favage appearance. Suffocating fumes of the burning heaps of copper arife in all parts, and extend their baneful influence for miles around. In the adjacent parts vegetation is nearly deftroyed; even the moffes and lichens of the rocks have perished: and nothing feems capable of refifting the fumes but the purple Melic grafs t, which flourishes in abundance.

I have little doubt but that the ore had been worked in a very diftant period. Veftiges of the antient operations appear in feveral parts, carried on by trenching, and by heating the rocks intenfe`y, then fuddenly pouring on water, fo as to caufe them to crack, or fcale; thus awkwardly fupplying the use of gunpowder 1. Pieces of charcoal were alfo found, which prove that wood was made use of for that purpofe. As the Britons imported all works in brafs, it is certain that the Romans were the undertakers of thefe mines; and it

* It is called Parry's Mountain, probably from Robert Parry, who was Chamberlain of North Wales, in the reign of Hen. IV.

† Melica Carulea, Lightfoot, Fl. Scot. i. 96. Aira Cærulea, HudJon, Fl. Ang. i. 33.

I SEE Tour in Wales, i. 52..

is very probable, that they fent the ore to Caerbên to be fmelted, the place where the famous cake of copper was difcovered §. They might likewife have had a fmelting hearth in this ifland; for a round cake of copper was difcovered at Llanvaetblle, a few miles from this place. Its weight was fifty pounds, and it had on it à mark refembling an L.

In the year 1762, one Alexander Frazier came into Anglesey in fearch of mines. He visited Parry's Mountain; called on Sir Nicholas Payley, and gave him fo flattering an account of the profpect, as induced him to make a trial, and fink fhafts. Ore was discovered; but before any quantity could be gotten, the mines were overpowered with water. In about two years after, Meffrs. Roe and Co. of Macclesfield applied to Sir Nicholas for a lease of Penryn ddu mine in Caernarvonshire; with which they were, much against their wills, compelled to take a lease of part of this mountain, and to carry on a level, and make a fair trial. The trial was accordingly made: ore was discovered; but the expences over balanced the profits. They continued working to great lofs: and at length determined to give the affair up. They gave their agent orders for that purpofe; but he, as a final attempt, divided his men into ten feveral companies, of three or four in a partnership, and let them fink shafts in various places, about eight hundred yards eallward of a place called the Golden Venture, on a prefump ion that a fpring, which iffued from near the place, must come from a body of mineral. His conjecture was right; for in lefs than two da s they met with, at the depth of feven feet from the furface, the folid mineral, which proved to be that vaft body which has fince been worked to fuch advantage. The day that this difcovery was made was March 2, 1768; which has ever fince been obferved as a feftival by the miners. Soon after this difcovery, another adventure was begun by the reverend Mr Edward Hughes, owner of part of the mountain, in right of his wife Mary Lewis of Llys Dulas; fo that the whole of the treasure is the property of Sir Nicholas Bayley, and himself.

The body of copper ore is of unknown extent. The thickness has been afcertained, in fome places, by the driving of a level under it, feveral years ago, and it was found to be in fome places twentyfour yards. The ore is moftly of the kind, called by Cronfled, Pyrites cupri flavo viridefcens; and contains valt quantities of fulphur. It varies in degrees of goodness; fome of it is rich, but the greater part poor in quality.

There are other fpecies of copper ore found here. Of late a vein of the Pyrites cupri grifeus of Cronfted, about feven yards wide, has been fcovered near the weft end of the mountain: fome is of an iron grey, fome quite black; the firft contains fixteen lb. of copper per clb. the laft, forty. An ore has been larely found, in form of loofe earth, of a dark purp'ist colour; and the best of it has produced better than eight in twenty. Some years ago, above thirty pounds of native copper was found in driving a level through a turbery; fome was in form of mofs, fome in very thin leaves.

§ Tour in Wales, p. 72. tab. ix.