In discussing poetry it is once more necessary to begin with something which will serve us as a definition. No man can imprison the essence of an art in words; and it is not to be understood that a formal definition can be framed which shall express all that poetry is and means. Its more obvious characteristics, however, may be phrased, and even an incomplete formula is often useful. There have been almost as many definitions of poetry made already as there have been writers on literature, some of them intelligible and some of them open to the charge of incomprehensibility. Schopenhauer, for instance, defined poetry as the art of exciting by words the power of the imagination; a phrase so broad that it is easily made to cover all genuine literature. It will perhaps be sufficient for our purpose here if we say that poetry is the embodiment in metrical, imaginative language of passionate emotion. By metrical language is meant that which is systematically rhythmical. Much prose is rhythmical. Indeed it is difficult to conceive of fine or delicate prose which has not rhythm to some degree, and oratorical prose is usually distinguished by this. The Bible abounds in excellent examples; as, for instance, this passage from Job:-- Hell is naked before Him, and destruction hath no covering; He stretcheth out the north over the empty place, and hangeth the earth upon nothing. He bindeth up the waters in his thick clouds; and the cloud is not rent under them. He holdeth back the face of His throne, and spreadeth His cloud upon it. He hath compassed the waters with bounds until the day and night come to an end. The pillars of heaven tremble, and are astonished at His reproof. He divideth the sea with His power, and by His understanding He smiteth through the proud.--_Job_, xxvi. 6-12. Here, as in all fine prose, there is a rhythm which is marked, and at times almost regular; but it is not ordered by a system, as it must be in the simplest verse of poetry. Take, by way of contrast, a stanza from the superb chorus to Artemis in "Atalanta in Calydon:"-- Come with bows bent and with emptying of quivers, Maiden most perfect, lady of light, With a noise of winds and many rivers, With a clamor of waters and with might; Bind on thy sandals, O thou most fleet, Over the splendor and speed of thy feet; For the faint east quickens, the wan west shivers, Round the feet of the day and the feet of the night. Here the rhythm is systematized according to regular laws, and so becomes metrical. The effect upon the ear in prose is largely due to rhythm, but metrical effects are entirely within the province of poetry.