in one sense, so the lives of eminent men, freely written, are truly the history of their times; and that no more authentic account of any age, its transactions, the springs which impelled men's conduct, and the merits which different actors in its scenes possessed, can be obtained than by studying the biography of the personages who mainly guided affairs, and examining their characters, which by their influence they impressed upon the times they flourished in. Such a work had moreover this advantage, that beside preserving the memory of past events, and the likeness of men who had passed from the stage, it afforded frequent opportunities of inculcating the sound principles of an enlightened and virtuous policy, of illustrating their tendency to promote human happiness, of exhibiting their power to exalt the genuine glory as well of individuals as of nations.

Though I could entertain little doubt that this plan was expedient, no one could more doubt than I did the capacity brought to its execution, or feel more distrustful of the pen held by a hand which had so long been lifted up only in the contentions of the Senate and the Forum. My only confidence was in the spirit of fairness and of truth with which I entered on the performance of the task; and I now acknowledge with respectful gratitude the favour which the work has hitherto, so far above its deserts, experienced from the public, both at home, in spite of party opposition, and abroad, where no such unworthy influence could have place. It is fit that I also express my equal satisfaction at the testimony which has been borne to its strict impartiality by those whose opinions, and the opinions of whose political associates, differed the most widely from my own. That in composing the work I never made any sacrifice of those principles which have ever guided my public conduct, is certain; that I never concealed them in

the course of the book is equally true; nay, this has been made a charge against it, as if I was at liberty to write the history of my own times, nay, of transactions in many of which I had borne a forward part, and not show what my own sentiments had been on those very affairs. But if my opinions were not sacrificed to the fear that I might offend the living by speaking plainly of the dead, so neither were truth and justice ever sacrificed to those opinions.

The Statesmen of George the Third's age having thus formed the subject of the volumes first published, I then gave a more full and elaborate view of the Learned Men who flourished in the same period. In my opinion, these, the teachers of the age, covered it with still greater glory than it drew from the Statesmen and the Warriors who ruled its affairs. It was necessary to enter much more into detail here than in the other branch of the work, because a mere general description of scientific or of literary merit is of exceedingly little value, conveying no distinct or precise idea of the subject sought to be explained. It appeared the more necessary to discuss these matters minutely, because upon some of them much prejudice prevailed, and no attempt had hitherto been made to examine them completely, or even impartially. Of this a remarkable example is afforded by the want of anything that deserves the name of a Life of Voltaire, and by the great prejudices, both favourable and unfavourable to him, which, among different classes, exist on the subject. But it must also be observed that Dr. Black's discoveries have been far from attaining the reputation which they so well deserve as the foundation of modern chemistry; and justice to this illustrious philosopher required that the consequences arising from his modesty and his great indifference to fame should be counteracted by a full history of his scientific labours, comparing the state of the science as he found it with that in which

he left it. My own personal acquaintance with some of the great men whose history I ventured to write, enabled me to throw additional light upon it; and respecting one, whom of course I could not have known, Mr. Hume, I obtained information from good sources through the kindness of friends. The materials of his life are, however, chiefly to be sought in his writings, and especially in his letters. The same remark is applicable to the Life of Voltaire. Those who have written it, like the Marquis de Condorcet, without ever referring to the fourteen large volumes (containing nine thousand closely-printed pages) of his Correspondence, might just as well have undertaken to give a life of Rousseau without consulting his Confessions,' or of Hume, without reading his 'Autobiography.'-I have, besides, had access to valuable original documents both of Voltaire, Robertson, and Cavendish; to some respecting Watt and Simson.

Scientific and literary history, the record of the progress of science and of letters, and which is most usefully given in the lives of their cultivators, serves two purposes; the one historical and critical, the other didactic. It is of great importance to trace the progress of mankind in the advancement of knowledge, and its diffusion; to show by what steps improvements have been made and applied; to estimate the relative merits of those whose claims upon our gratitude are the most unquestionable; and to ascertain the position in which their labours have left the subjects of those labours, with the aspect and extent of the region that yet remains unexplored. But, it is hardly a less valuable service of such works that they promote the knowledge of the subject matter, both by exciting the desire of it, and by facilitating its acquisition. The history of a philosopher's life, that is, of his labours, the tracing of those steps by which he advanced beyond his predecessors, the com

parison of the state of the science as he found it, with that in which he left it, tends mightily to interest the reader, to draw him towards the same inquiries, and to fix his views more closely upon the details of the subject, if it has already somewhat occupied his mind. In like manner, the recording and the description of literary labours and merits, in connexion with the historians, poets, and orators themselves, has a powerful effect in making the reader familiar with the subject, while it cultivates and refines his taste.

Under the head of Philosophers, it is unnecessary to observe upon any of the lives except those of Adam Smith, D'Alembert, and Simson, except to note, that those of Black and Lavoisier give a full statement of the relative merits of these great men, and of the conduct of the latter, both with regard to Black and Priestley. But as many persons entertain a prejudice against the pretensions, or it may be, against the practical conclusions of the Political Economists, they may be apprised that the subjects on which the great and well-established fame of Adam Smith is founded, are here treated without any of the exaggerations wherewith speculative economists have been charged, and that the Life, and the Analysis of his great work were written long before the question respecting Free Trade and the repeal of the Corn Laws had assumed a practical form. Whatever touches that question, was composed as a treatise upon a subject of science only, with the desire to discover and to expound the truth, and without any view to the interests of any party,-the author, though he entirely approved the repeal, yet neither agreeing with those who hoped, nor with those who feared, so much from its consequences.

The Lives of Simson and D'Alembert, are designed not only to give the history of these eminent men-the restoration of the ancient geometry by the former, and the improve

ment of the modern analysis by the latter-but also to convey a competent knowledge of those great methods; while in both lives, especially that of D'Alembert, there is further presented a strong recommendation of mathematical pursuits, by showing the gratification which they are fitted to bestow. Great as is the value of Montucla's History, in the light of a didactic work, many readers have lamented not more that he left it unfinished, and the latter half very unsatisfactorily edited, than that he did not enter more fully into the detailed statement of the subject, in several of the earlier portions.

By such historical and critical works, then, the desire and the acquisition of science is promoted; and surely no more important duty can be performed, than that of affording both the excitement and the gratification, in however moderate a degree. They who are wholly incapable of advancing science themselves, may help others to the knowledge of what the great masters have done; and they may do this best by not disdaining the office of elementary explanation and discussion. Two thousand years ago, the wisest of the ancients was said to have brought philosophy down from heaven to earth; certainly, he chiefly valued himself on his constant efforts to stir up in men's minds the desire of knowledge.* What he found necessary with regard to the nature of the subject, we in our day may perceive to be equally necessary because of the clouds in which great men, almost unavoidably, involve their scientific researches. The mathematical writings of Newton and his immediate successors require to be made plain, and also to be illustrated by comparative discussion, in order both to show exactly what they accomplished, and to excite an intelligent curiosity respecting their labours. This has been

* Cic. Acad., Qu. i. 4, Tusc. v. 4.