PROMETHEUS                                          *552                                           PROTAGORAS

use. Chain-shot, bar-shot, carcass and light-ball are other varieties which are now obsolete. There are three varieties of the oblong projectiles: the solid shot, the hollow shot or the shell and the case-shot. The hollow shot contains some explosive which, at some point in its course, is ignited by a fuze or other means. Case-shot comprise grape-shot, canister and shrapnel, and are used against animate objects. Oblong projectiles have many advantages over spherical projectiles. They are in use confined to rifled guns.

Prometheus (prō-m'thūs), a hero of Grecian mythology, who, on account of various services rendered to men, was chained by Zeus to a rock, where a vulture was sent to devour his liver by day, Zeus causing it to grow again by night. As Prometheus continued to endure this torture without yielding, the wrath of Jupiter was at length appeased, and the victim was released. Some legends represent the offense of Prometheus as stealing fire from heaven for the benefit of men; and in the tragedy of schylus he is an immortal god, a friend of the human race, who does not shrink from opposing the evil designs of Zeus against mankind nor even from sacrificing himself for their salvation. The possession of fire was very important to the early races of men, and the legend of its having been originally stolen from heaven is very widely spread over the world.

Proof'-Read'ing. Owing to the varieties of handwriting which are submitted to printers, as well as to various accidents which cannot wholly be avoided in setting up type, it is necessary that the first imprints or proofs of a book or periodical should be carefully revised and corrected Moreover, an author or editor is by this means enabled to make alterations or corrections in the text to the last moment. Among the errors for which proof-readers will be on the alert are these : the omission of letters or their wrongful insertion; bad spacing between words or letters ; the omission of words; the transposition of letters, words or phrases; wrong type; defective punctuation and use of capitals; crookedness of lines. For t'.ese faults the proofreader uses certain appropriate marks. It is not, however, necessary to a,dhere to these marks alone. Every proof-reader should, however, make his correctionsin the margin and on the side nearest the error. He should set a vertical stroke at the end of each correction in the margin. The spot at which the correction is to be made should also be indicated. The purpose of the vertical stroke after each marginal correction is to separate one correction from another, for it is not uncommon to find several fall close together, even in the one line. Thus a wrong letter would be corrected by a

stroke through it, the right letter written in the margin, and a vertical stroke after this letter A caret is used where something is to be inserted; a mark like a d where something is to be deleted or omitted. Proof-reading must be done with attention to the form rather than the meaning, except where the editor or author may wish to make alterations in the meaning rather than to correct the form. It is difficult and unsafe to attempt to combine both purposes in a single reading. In general, even the form requires three readings, preferably by at least two different persons.

Prop'aga'tion, as a natural process among wild plants, is accomplished by the various methods of scattering spores (q. v.) and seeds (see Seed-Dispersal), through parts of plants, as buds and twigs, breaking ff and taking root or even by the entire plant being carried by the wind, as such "tumble-weeds" as the Russian thistle and pigweed. Other means of propagation are runners and branches that take root at their joints or tips, as the strawberry and raspberry. Many plants spread only too effectively through shoots sent up by their roots and underground stems, as the silver-leaf poplar and Canadian thistle. But in the horticultural sense propagation refers to a group of artificial processes, as budding, grafting and layering (see these headings), the planting of seeds, bulbs, tubers, cuttings etc. or the transplanting of young plants (see Hot-Bed). The reproduction of plants by other means than from the seed is spoken of as vegetative propagation, and is used to keep some desirable characteristic that will not breed "true" in seedlings, as m fruit-trees. (See Grafting.) For the manner in which new varieties are produced see Plant-Breeding.

Prosenchyma (prŏs-ĕti'kĭ-m) (in plants), a tissue in plants whose cells are elongated or fibrous. It is a general name covering all elongated and fiber-like cells, as distinct from parenchyma, which is a tissue composed of cells whose three diameters are approximately the same.

Proserpina (pr-sr'p-n), daughter of Zeus and Demeter. While gathering flowers on the plains of Sicily, she was abducted b> Pluto and taken to his abode in the underworld, where she was found by her mother after a nine-years' search, and given up by Pluto only on condition that she live underground for part of the year. The myth clearly is an expression of the revival of nature every year, after winter is over.

Protagoras (pr-tg'-r s), the earliest of the Greek sophists, was a native of Ab-dera, born about 481 B. C. The basis of his philosophy is the proposition that "man is the measure of all things." All his works are lost, and he himself perished at sea (c. 411) while on his way to Sicily to scap a charge of atheism brought against him at Athens.