The following allufion, in one of Mr. Home's tragedies, appears to me to unite almost excellence: every "Hope and fear, alternate, sway'd his breast; Here the analogy is remarkably perfect; not only between light and hope, and between darkness and fear; but between the rapid fucceffion of light and shade, and the momentary influences of these oppo. fite emotions: while, at the fame time, the new image which is prefented to us, recals one of the most pleafing and impreffive incidents in rural scenery. The foregoing obfervations fuggeft a reason why the principal ftores of Fancy are commonly fuppofed to be borrowed from the material world. Wit has a more extensive province, and delights to display it's power of prompt and unexpected combination over all the various claffes of our ideas: but the favourite excurfions of Fancy, are from intellectual and moral fubjects to the appearances with which our fenfes are converfant. The truth is, that fuch allufions please more than any others in poetry. According to this limited idea of Fancy, it prefuppofes, where it is pof. feffed in an eminent degree, an extenfive obfervation of natural objects, and a mind susceptible of strong impreffions from them. It is thus only that a flock of images can be acquired; and that these images will be ready to present themselves, whenever any analogous fubject occurs. And hence probably it is, that poetical genius is almost always united with an exquifite fenfibility to the beauties of nature. Before Before leaving the fubject of Fancy, it may not be improper to remark, that its two qualities are, livelinefs and luxuriancy. The word lively refers to the quickness of the affociation. The word rich or luxuriant, to the variety of affociated ideas. IV. Of Invention in the Arts and Sciences. To these powers of Wit and Fancy, that of Invention in the Arts and Sciences has a ftriking resemblance. Like them it implies a command over certain claffes of ideas, which, in ordinary men, are not equally fubject to the will: and like them, too, it is the refult of acquired habits; and not the original gift of nature. Of the process of the mind in fcientific invention, I propofe afterwards to treat fully, under the article of Reasoning; and I fhall therefore confine myself at present to a few detached remarks upon fome views of the fubject which are fuggefted by the foregoing inquiries. Before we proceed, it may be proper to take notice of the diftinction between Invention and Difcovery. The object of the former, as has been frequently remarked, is to produce fomething which had no existence before; that of the latter, to bring to light something which did not exist, but which was concealed from common obfervation. Thus we fay, Otto Guerricke invented the air-pump; Sanctorius invented the thermometer; Newton and Gregory invented the reflecting telescope; Galileo difcovered the folar spots; and Harvey difcovered the circulation of the blood. blood. It appears, therefore, that improvements in the Arts are properly called inventions; and that facts brought to light by means of obfervation, are properly called difcoveries. Agreeable to this analogy, is the ufe which we make of these words, when we apply them to fubjects purely intellectual. As truth is eternal and immutable, and has no dependence on our belief or difbelief of it, a person who brings to light a truth formerly unknown, is faid to make a discovery. A perfon, on the other hand, who contrives a new method of discovering truth, is called an inventor. Pythagoras, we fay, discovered the forty-feventh propofition of Euclid's first book; Newton difcovered the binomial theorem: but he invented the method of prime and ultimate ratios; and he invented the method of fluxions. In general, every advancement in knowledge is confidered as a difcovery; every contrivance by which we produce an effect, or accomplish an end, is confidered as an invention. Difcoveries in fcience, therefore, unless they are made by accident, imply the exercise of invention; and, accordingly, the word invention is commonly ufed to exprefs originality of genius in the Sciences, as well as in the Arts. It is in this general fenfe that I employ it in the following obfervations. It was before remarked, that in every inftance of invention, there is fome new idea, or fome new com. bination of ideas, which is brought to light by the inventor; and that, although this may fometimes happen, in a way which he is unable to explain, yet when when a man poffeffes an habitual fertility of invention in any particular Art or Science, and can rely, with confidence, on his inventive powers, whenever he is called upon to exert them; he must have acquired, by previous habits of study, a command over thofe claffes of his ideas, which are fubfervient to the particular effort that he wishes to make. In what manner this command is acquired, it is not poffible, perhaps, to explain completely; but it appears to me to be chiefly in the two following ways. In the first place, by his habits of fpeculation, he may have arranged his knowledge in fuch a manner as may render it eafy for him to combine, at pleasure, all the various ideas in his mind, which have any relation to the subject about which he is occupied: or, fecondly, he may have learned by experience, certain general rules, by means of which, he can direct the train of his thoughts into those channels in which the ideas he is in queft of may be most likely to occur to him. I. The former of these obfervations, I fhall not stop to illuftrate particularly, at present; as the fame fubject will occur afterwards, under the article of Memory. It is fufficient for my purpose, in this chapter, to remark, that as habits of fpeculation have a tendency to claffify our ideas, by leading us to refer particular facts and particular truths to general prin. ciples; and as it is from an approximation and comparison of related ideas, that new difcoveries in moft inftances refult; the knowledge of the philofopher, even supposing that it is not more extensive, is arranged in a manner much more favourable to invention, than in a mind unaccustomed to fyftem. How much invention depends on a proper combination of the materials of our knowledge, appears from the resources which occur to men of the lowest degree of ingenuity, when they are preffed by any alarming difficulty and danger; and from the unex. pected exertions made by very ordinary characters, when called to fituations which roufe their latent powers. In fuch cafes, I take for granted, that neceffity operates in producing invention, chiefly by concentrating the attention of the mind to one fet of ideas; by leading us to view these in every light, and As the to combine them variously with each other. fame idea may be connected with an infinite variety of others by different relations; it may, according to circumftances, at one time, fuggeft one of these ideas, and, at another time, a different one. When we dwell long on the fame idea, we obtain all the others to which it is any way related; and thus are furnished with materials on which our powers of judgment and reasoning may be employed. The effect of the divifion of labour, in multiplying mechanical contrivances, is to be explained partly on the fame principle. It limits the attention to a particular fubject, and familiarifes to the mind all the poffiany ble combinations of ideas which have relation to it. These observations fuggeft a remarkable difference between Invention and Wit. The former depends, in moft inftances, on a combination of thofe ideas, which are connected by the less obvious principles of affociation; and it may be called forth in almost any mind by the preffure of external circumftances. The |