V.

CHA P. tion dwells more habitually on human life and conduct, than on the material objects around him. This is the cafe with the banished Duke, in Shakespeare's As you like it, who, in the language of that Poet,

"Finds tongues in trees, books in the running brooks,
<< Sermons in ftones, and good in every thing."

But this is plainly a diftempered ftate of the mind; and the allusions please us, not so much by the analogies they present to us, as by the picture they give of the character of the perfon to whom they have occurred.

2. AN allusion pleases, by presenting a new and beautiful image
to the mind. The analogy or the resemblance between this
image and the principal fubject, is agreeable of itself, and is
indeed neceffary, to furnish an apology for the transition which
the writer makes; but the pleasure is wonderfully heightened,
when the new image thus prefented is a beautiful one. The
following allufion, in one of Mr. Home's Tragedies, appears to
me to unite almost every
excellence :

Hope and fear, alternate, sway'd his breast;
"Like light and shade upon a waving field,
"Courfing each other, when the flying clouds

"Now hide, and now reveal, the Sun."

HERE the analogy is remarkably perfect; not only between light and hope, and between darkness and fear; but between

the

309

V.

the rapid fucceffion of light and shade, and the momentary CHA P. influences of these oppofite emotions: and, at the fame time, the new image which is prefented to us, is one of the most beautiful and striking in nature.

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 make new combinations, whatever be the nature of the compared ideas: but the favourite excurfions of Fancy, are from intellectual and moral subjects 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 presupposes, where it is poffeffed in an eminent degree, an extensive observation of natural objects, and a mind fufceptible of ftrong impreffions from them. It is thus only that a stock 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 exquisite sensibility to the beauties of nature.

BEFORE leaving the fubject of Fancy, it may not be improper to remark, that its two qualities are, liveliness and luxuriancy. The word lively refers to the quickness of the affociation. The word rich or luxuriant to the variety of affociated ideas.

CHA P.
V.

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 striking refemblance. 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.

Or the process of the mind in scientific invention, I propose afterwards to treat fully, under the article of Reasoning; and I shall therefore confine myself at prefent 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 distinction between Invention and Discovery. 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 fomething which did exift, 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 fpots; and Harvey discovered the circulation of the blood. It appears, therefore, that improvements in the Arts are properly called inventions ; and that facts brought to light by means of observation, are properly called difcoveries.

AGREEABLE

V.

AGREEABLE to this analogy, is the ufe which we make of CHA P. these words, when we apply them to fubjects purely intellectual. As truth is eternal and immutable, and has no dependence on our belief or disbelief 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-seventh propofition of Euclid's firft book; Newton discovered 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 discovery; every contrivance by which we produce an effect, or accomplish an end, is confidered as an invention. Discoveries in science, therefore, unless they are made by accident, imply the exercife of invention; and, accordingly, the word invention is commonly used 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 combination 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 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,

V.

CHA P. ftudy, a command over those claffes of his ideas, which are fubfervient to the particular effort that he wifhes to make. In what manner this command is acquired, it is not possible, 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 easy 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.

1. THE former of thefe obfervations, I fhall not stop to illustrate particularly, at prefent; 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 speculation have a tendency to claffify our ideas, by leading us to refer particular facts and particular truths to general principles; and as it is from an approximation and comparison of related ideas, that new discoveries in most 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