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* BOILEAXJ-DESPREATJX. 237 BOILER. mand of the King, who made him a royal histo- riographer, and he died at Auteuil, March 13, 1711. His satire on the vices of Paris was his first success, and by its date gave a name to the 'school of 10(10.' Seven other satires appeared in 16G6, and five more complete the list. They are in rhymed couplets, polished, harmonious, witty, with the maliciousness of merciless per- sonalities. This was destructive criticism with a vengeance. In the Art poetiqtie (1074) he was constructive, and, following Horace's Arx Porti- ca, gave a theory of poetic composition in four cantos, of which the first lays down general ndes, the second applies these to lyric poetry, the third to the epic and the drama, while the fourth contains general reflections, advice, and cautions. all spiced with brilliant wit and barbed with personal allusiim. He preached a reign of lit- erary law, truth in subject, conscientious work- manship in form, unity, clearness, proportion. He sought to establish literature on an un- changing foundation and to give canons of clas- sicism for the ages. And indeed his work has a perennial reasonableness, though it allowsseant scope for ''the heat and height of sane emo- tion" and the unchartered play of genius. For Boileau's mind was material, logical, lacking in The best edition of Boileau's Tl'orfcs is by Gidel, 4 vols. (1870-73). Consult: Deschanel, /^e ronian- lisme des classigucn, 4th series (Paris, 1888); Lansou, Boi'rnu (Paris, 1892) ; Morillot, Boi- Icnii (Paris. 1892) ; Faguet. XYIT. Siecle. Etudes litlcralrrx (Paris, 1887): Henion, Cours de lit- tenilurr (Paris, 1889-95). BOILER. In steam engineering, a vessel in which steam is generated at a high pressure for heating or power purposes. In its simplest form, it consists of a closed vessel made of sheet metal, having apertures for the admission of water and egress of steam, fitted with appara- tus for showing the level of the water and the pressure of the steam, and set or mounted in combination with a furnace, either internal or external. When water is boiled in an open pan, the temperature of the water and of the steam rising from it remains at, or very near, 212° F., and the tension or pressure of the steam is no more than sufficient to make its way into the atmosphere, being exactly equal to that ex- erted in all directions by the atmosphere itself — namely, 14.7 pounds per square inch. In a closed vessel, on the other hand, the tempera- ture and pressure to which we can raise the steam are only limited by the strength of the DOUBLE-FLUE BOILEB. imagination. He has been studied by generations because his is the art that can be learned, as Pope, his best pupil, learned it, though his own Horace might have taught him that the true poet could not be made. Boileau repeated and enforced his critical views in the prose Dialogue des hcros de romaii, whose authorship he at first concealed, and in Reflexions critiques sur Longin (1693). His o i best verses are twelve Epitres and a mock-heroic epic, he lutriti. which was liis most popular work. It was published in part in 1G73, but not in full till after his death. This and all the poems are filled with cleverly turned lines that remain as familiar quotations, but Boileau should be most gratefully remembered as the first systematic critic of France, the first to make criticism an art. He was narrow and some- times unjust, he never fully grasped the funda- mental principles of the classic art he admired; but his honest, loyal, stubborn, rough good sense did much to direct the talent of Moli^re, Racine, and La Fontaine to its most fruitful channels and to guide the next generation to a true, though partial, naturalism. On the lyric poetry of suc- ceeding generations its effect was to cultivate a formal technique and so to check inspiration that first fullv revives in the Romantic School. vessel or boiler against bursting. The form of a boiler is determined by two considerations — ■ namely, strength to withstand internal pressure, and efficiency in producing steam ; and the ob- ject of the designer is to combine in one appara- tus sufl!ieient strength to work safely at the proposed pressure, with such a form and arrange- ment as shall abstract the maximum of heat from the gases of combustion, and at the same time bo in all respects suitable to I lip special circumstances of the case. The globular form is that best adapted for strength, and was the earliest to be used. It presents to the fire, however, the minimum area in proportion to its contents, and therefore has a mininmm effi- ciency. After spherical boilers, cylindrical ones came into use, at first set on end. and after- wards laid on their sides, and later on these v.ere furnished with internal cylindrical tubes for furnaces. Watt's 'wagon boiler' (so called from its shape) was used for many years, but being quite iinfit for any but the lowest pres- sures, it has long been discarded ; and the 'egg- end' boiler, or plain cylinder with hemispherical ends, also much used at one time, has now almost disappeared on account of its small evapo- rative efficiency, it being used only where large