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which were of importance, from his own recollection of incidents, cafually fet down.

• There are fome in which he feems to have inferted every thing as it took bis faney, in medicine, chemistry, jurisprudence, or matters of tate; and I find others into which he has transferred the fame things, but bas diftributed them according to their feientific connexions. In fhort, he has kept a journal and leger of his audies, and has pofted his books like a merchant. I have locked over thefe memorandums with fome care, and have there feen the firft germs of those discoveries which have at last produced fuch a complete revolution in chemical fcience. What particularly ftruck me, was the fleadiness with which be advanced in any path of knowledge,-ulla retrarfum. Things are inferted for the firit time, from fome prefent impreffion of their fingularity or importance, but without any allufion to their connexions. When a thing of the fame kind is mentioned again, there is generally a reference back to its fellow; and thus the most infulated facts often acquired a connexion which gave them fcientific importance. Preface, p. xxii. xxiii.

Mr Robifon has performed the duty entrusted to him by his friend's executors, in fuch a manner as muit entitle him not merely to their thanks, but to the lafting gratitude of the fcientific world. He has prefented us with a very full, and apparently a very accurate collection, of the most valuable parts of the lectures, as nearly as posible in the very words of the teacher. He has faithfully adhered to the arrangement of the courfe, except in two inftances, where a fight charge feems to be perfectly justified by the convenience which attends it. His preface contains a clear and compendious account of the import of Dr Black's difcoveries, and a very interesting sketch of his life. In the foot-notes, he has occafionally added to the rich collection of facts and obfervations contained in the text, feveral valuable remarks and statements fuggefted by his own experience. In the more copious notes fubjoined to each volume, he has introduced various difcuffions of the highest importance both to the elucidation of the general fubject, and the eftablishment of leading points in the history of the fcience. Let our scientific readers confider, how much of all this confifts in mere labour, unrepaid by the peculiar reward of genius; and let them remember that Mr Robifon's talents are as original as his acquirements are various and profound: they will then be able to eftimate the extent of the obligations under which he has laid them by editing this valuable work."

It would be perfectly inconfiftent with our plan, and far exceed our limits, to analyze thefe lectures, or the commentaries of the editor, which, like the text, must neceffarily be very mifcellaneous. We fhall confine ourselves to a few general obfervations on each of the two departments; and fhall, in the firft place, endeavour to make our readers acquainted with the illuf

trious man whofe life and difcoveries confer upon the present publication its chief interest.

Jofeph Black was fprung from a Scotifh family, tranfplanted firft to Ireland, and then to France, the country which gave him birth. He spent, in Bordeaux and its vicinity, thofe years of infancy devoted by the conftitution of human nature to imbecility, thraldom and ignorance, and extolled, by the general confent of mankind, as the feafon of genuine happinefs. The biographer has wifely paffed over the hiftory of this blifsful period, and preferred dwelling upon thofe fcenes which difplay the ripened powers of the mind. After an account of the intimacy which fubfifted between the amiable parents of the philofopher and the celebrated prefident Montefquieu, the narrative is purfued from the period of Dr Black's removal to Belfaft, in the twelfth year of his age. He there received the rudiments of his literary education, and finished it at the University of Glafgow, the fcene of his future discoveries. His attention appears to have been divided between the science which his natural bias led him peculiarly to cultivate, and those more general objects of fpeculation which enlarge the understanding, while they improve the tafte. Although his application to thefe delightful purfuits was never very ardent, it was steady and vigorous. If he did not, like Pafcal, Newton, M'Laurin, and various writers on lighter fubjects, astonish the world by a premature difplay of talents, his want of those stronger paffions, which lead to an early developement of genius, infured him the poffeffion of a calm and immoveable judgement, a patient capacity of observation, and a modest distruft of theory, -the moft effential characteristics of the inductive philofopher.

In the course of his ftudies, he does not appear to have entered deeply into the abstract fciences, either of mathematical or metaphyfical truth. His tafte led him rather to the contemplation of real and external objects; and he foon employed as much of his talents as he ever devoted to fevere ftudy, in the inveftigations of experimental philofophy. The phyfical difcoveries of Sir Ifaac Newton attracted his chief admiration; and, upon the unequalled models of inductive difquifition which the treatife of Light contains, his fcientific habits were happily formed. After he had, by his own difcoveries, laid the foundation of a revolution in fcience, almost equal to the changes which his great mafter had effected, we find him fteadily perfevering in the fame trict and chastened fyftem of inductive logic, and freely acknowledging the fources of his fkill.

My acquaintance with him (fays Mr Robifon) began at Glasgow in 1758, I being then a ftudent in that Univerfity; and it began in a way which marked the diftinguifted amiablenefs of his difpofition and be

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haviour. It was at the house of one of the profeffors, to whom I was telling the great entertainment I had received from the lectures of Dr Robert Dick, Profeffor of Natural Philofophy, and how much I admired him as a lecturer. Dr Black joined in the commendation; and then, addreffing himself to me, queftioned me a good deal about natural philofophy, fo as to perceive what were the peculiar objects of my attention. His advices relative to my favourite ftudy were fo impreffive, and given in a manner fo unaffectedly serious and kind, that they are ftill as fresh in my mind as if of yefterday's date. I was a ftranger to him, and not even his pupil; and he was prompted to take that pains with me, folely by the way in which he heard me fpeaking of the lectures of one whom he loved and efteemed. Gently and gracefully checking my difpofition to form theories, he warned me to fufpect all theories whatever, preffed on me the neceffity of improving in mathematical knowledge, and gave me Newton's Optics to read, advifing me to make that book the model of all my ftudies, and to reject, even without examination, every hypothetical explanation, as a mere waste of time and ingenuity. Preface, p. vii.

The profeffion of medicine, which Dr Black chose from its confonance with the tenour of his favourite ftudies, was extremely unfuitable to his delicate conftitution, and the amiably folicitous temper of his mind. The duties of his ftation as a physician, and of his three fucceffive profefforfhips, were, unfortunately for science, (we may add, for his own fame), matters of fuch anxious care, as to diftract much of his attention from the path of original inveftigation, which he had entered with the moft fplendid profpects of fuccefs. The doctrine of latent heat appears to have been early familiar to his thoughts. In the oldeft parcels of his notes, Mr Robifon found queries relative to this point; and Dr Black himself afferts, (vol. I. p. 156.), that he can fcarcely remember the time when he had not fome idea of the disagreement of the facts with the common doctrines of heat. The extracts from the memorandum-books given in these volumes, fufficiently prove, that, while a ftudent, his ideas had been fomewhat matured upon the fubject. Before the year 1763, his whole experiments and inquiries on the absorption of heat, were brought to a conclufion; and his inaugural differtation, when he received a degree in 1754, contained an account of his other grand difcovery-the nature of the alkaline earths, and the properties of fixed air. He removed from Glafgow to Edinburgh in 1766, and died in 1799. How great a part, then, of this most valuable life was fpent in the mere exercise of profeffional duties! At an age when the bulk of philofophers are only beginning to ftrike out new lights, Black had closed his fhort career of brilliant difcovery; entered upon the common task of a chemical teacher; limited his ambition to the fimple explication of a science which

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he might have created anew; and left to his more ardent, or more fortunate fucceffors, the glories of rearing a fyftem, of which he had laid the firm foundations, and furnifhed the chief materials. We shall afterwards fee, that they are charged with refufing to engrave his name upon the ftructure, and to beftow his' portion of honour on him whofe genius and ill fate had left them fo ample a fhare.

In contemplating the intellectual character of this eminent per-. fon, we cannot fail to be delighted with the observation of that unity which feems peculiar to minds of the first order. An original genius is often to be found in all the departments of human excellence. But it is rarely, indeed, that we can discover one whofe features are at once diftinctly marked, and nicely blended; each different from the ordinary caft, and all animated by the fame fpirit. The moft aftonishing intellect that has ever been permitted to enlighten mankind, poffeffed this rare harmony in the very highest degree. Thofe qualities which diftinguished the father of inductive fcience from every other philofopher, were equally confpicuous in each of his various exertions; and the preeminent dignity of his powers was fuftained through all the thousand operations by which he enlarged the grafp of the human mind. It is in vain that we fearch every corner of the Newtonian writings, for fome trifling proof that their author was, like ourselves, liable to the common intellectual failings of the fpecies. We are confoled by no glimpse of wavering steps, even on the most delicate ground; or hafty advances, where the footing is fureft, and the prize most attractive; or carelefs examination, where the intermediate objects are moft trivial; or relaxation, when the greatest obstacles have been furmounted; or intemperate triumph, when the most dazzling profpects are displayed. Each height is reached by the fafeft and the fhortest path, with the fmalleft buftle; and the attainment is only valued as leading to fome loftier eminence. Each pofition is alike marked by its diftance from the ordinary level; by the nature of the works which fecure it, and of the country which it commands. The chief characteristic of Newton, is the degree of fuperiority in which he towers above every other natural philofopher, fo as to form a clafs by himself. But the kind of his excellence is alfo remarkable and uniform. The distance and diffimilarity of the objects which his difcoveries enable us to compare, is not more aftonithing, than the eafe and fimplicity of the means of comparifon. The pleasure of contemplation, which forms the primar object of all abftract fcience, and which the view of thofe comparitons invariably bestows, is equalled by the practical importance of the confequences to which they may be applied. The enunciation of the propofition is not

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more unexpected, than the demonftration is flowing, and the corollaries useful. All thofe various inveftigations, too, are the eafy and natural work of one great, fimple mind, verfatile in the direction of its efforts, but uniform in its mode of operation; not the attempts of an ordinary intellect, training at universality by ambitious mimicry of different talents.

In thefe particulars, we cannot avoid obferving a ftriking analogy between the philofophical genius of Black and that of NewNone of this illuftrious man's followers has fo correctly feized the true spirit of inductive reasoning by which he was guided, or combined fo happily the utmoft fimplicity of means with the accomplishment of the most difficult and important ends. In all Dr Black's analytical inquiries, we perceive how much be longs to the mind of the obferver; how little is left to the trick and dexterity of the operator. By placing nature in new combinations of circumftances, he extorts from her (to ufe the language of Lord Bacon) fome of her fublimeft fecrets: But thefe combinations are always fimple and conclufive. He knows, too, that the ordinary combinations which we witnefs every hour, require only patient obfervation, to furnish the unbiaffed reafoner with ample opportunities of generalization. Accordingly, in no fcientific inquiries, fince the date of the Principia and Optics, do we find fo great a proportion of pure ratiocination, founded upon the defcription of common facts, but leading to the moft unexpected and important refults, as in the two grand fyftems of Black. This mode of inveftigating, the laws of nature has various advantages of the highest confequence. It diminishes incalculably the chances of mistake, by precluding the ufe of complicated apparatus. It brings home to every one the evidence of the dif coveries, and expofes the demonftration of each propofition to the moft fevere and univerfal fcrutiny. It opens, to all who can obferve and reafon, the field of important inquiry, and raises the mind to the moft general views of the conftitution of the world. ` The fame happy turn of mind which placed the fcientific investigations of Dr Black fo near the greateft difcoveries that have ever been made by the fpecies, was perceptible alfo in the elegance and ingenuity which it mingled with all his perfonal habits.

I have already obferved,' fays Mr. Robifon that when I was first acquainted with Dr Black, his afpect was comely and interefting. As he advanced in years, his, countenance continued to preferve that pleafing expreffion of inward fatisfaction, which, by giving cafe to the beholder, never fails to pleafe. His manner was perfectly eafy, and unaffected, and graceful. He was of most easy approach, affable, and readily entered into converfation, whether ferious or trivial. His mind

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