FORE:(1.) In comparing steam-hammers with trip or crank hammers what mechanism does steam supplant or represent?(2.) What can be called the chief distinction between steam and other hammers?(3.) Under what circumstances is an automatic valve motion desirable?(4.) Why is a dead or uncushioned blow most effective?(5.) Will a hammer operate with air the same as with steam?We have seen how Epicurus erected the senses into ultimate arbiters of truth. By so doing, however, he only pushed the old difficulty a step further back. Granting that our perceptions faithfully correspond to certain external images, how can we be sure that these images are themselves copies of a solid and permanent reality? And how are we to determine the validity of general notions representing not some single object but entire classes of objects? The second question may be most conveniently answered first. Epicurus holds that perception is only a finer sort of sensation. General notions are material images of a very delicate texture formed, apparently, on the principle of composition-photographs by the coalescence of many individual images thrown off from objects possessing a greater or less degree of resemblance to one another.186 Thought is produced by the contact of such images with the soul, itself, it will be remembered, a material substance.
FORE:There was a time when mortals lived like brutesBut the enthusiasm for science, however noble in itself, would not alone have sufficed to mould the Epicurean philosophy into a true work of art. The De Rerum Natura is the greatest of all didactic poems, because it is something more than didactic. Far more truly than any of its Latin successors, it may claim comparison with the epic and dramatic masterpieces of Greece and Christian Europe; and that too not by virtue of any detached passages, however splendid, but by virtue of its composition as a whole. The explanation of this extraordinary success is to be sought in the circumstance that the central interest whence Lucretius works out in all directions is vital rather than merely scientific. The true heroine of his epic is not Nature but universal lifehuman life in the first instance, then the life of all the lower animals, and even of plants as well. Not only does he bring before us every stage of mans existence from its first to its last hour106 with a comprehensiveness, a fidelity, and a daring unparalleled in literature; but he exhibits with equal power of portrayal the towered elephants carrying confusion into the ranks of war, or girdling their own native India with a rampart of ivory tusks; the horse with an eagerness for the race that outruns even the impulse of his own swift limbs, or fiercely neighing with distended nostrils on the battlefield; the dog snuffing an imaginary scent, or barking at strange faces in his dreams; the cow sorrowing after her lost heifer; the placid and laborious ox; the flock of pasturing sheep seen far off, like a white spot on some green hill; the tremulous kids and sportive lambs; the new-fledged birds filling all the grove with their fresh songs; the dove with her neck-feathers shifting from ruby-red to sky-blue and emerald-green; the rookery clamouring for wind or rain; the sea birds screaming over the salt waves in search of prey; the snake sloughing its skin; the scaly fishes cleaving their way through the yielding stream; the bee winging its flight from flower to flower; the gnat whose light touch on our faces passes unperceived; the grass refreshed with dew; the trees bursting into sudden life from the young earth, or growing, flourishing, and covering themselves with fruit, dependent, like animals, on heat and moisture for their increase, and glad like them:all these helping to illustrate with unequalled variety, movement, and picturesqueness the central idea which Lucretius carries always in his mind.