Numerous editions of Boileau's works were published during his lifetime. The last of these, _Oeuvres diverses_ (1701), known as the "favourite" edition of the poet, was reprinted with variants and notes by Alphonse Pauly (2 vols., 1894). The critical text of his works was established by Berriat Saint-Prix, _Oeuvres de Boileau_ (4 vols., 1830-1837), who made use of some 350 editions. This text, edited with notes by Paul Cheron, with the _Boloeana_ of 1740, and an essay by Sainte-Beuve, was reprinted by Garnier _freres_ (1860). See also Sainte-Beuve, _Causeries du lundi_, vol. vi.; F. Brunetiere, "L'Esthetique de Boileau" (_Revue des Deux Mondes_, June 1889), and an exhaustive article by the same critic in _La Grande encyclopedie_; G. Lanson, _Boileau_ (1892), in the series of _Grands ecrivains francais_. BOILER, a vessel in which water or other liquid is heated to the boiling point; specifically, the apparatus by which steam is produced from water, as one step in the process whereby the potential energy of coal or other fuel is converted into mechanical work by means of the steam-engine. Boilers of the latter kind must all possess certain essential features, whilst of other qualities that are desirable some may not be altogether compatible with the special conditions under which the boilers are to be worked. Amongst the essentials are a receptacle capable of containing the water and the steam produced by its evaporation, and strong enough continuously to withstand with safety the highest pressure of steam for which the boiler is intended. Another essential is a furnace for burning the fuel, and a further one is the provision of a sufficiency of heating surface for the transmission of the heat produced by the combustion of the fuel to the water which is required to be evaporated. Desirable qualities are that the arrangements of the furnaces should be such that a reasonably perfect combustion of the fuel should be possible, and that the heating surfaces should be capable of transmitting a large proportion of the heat produced to the water so as to obtain a high evaporative efficiency. Further, the design generally should be compact, not too heavy or costly, and such that the cleaning necessary to maintain the evaporative efficiency can be easily effected. It should also be such that the cost of upkeep will be small, and that only an average amount of skill and attention will be required under working conditions. It is for providing these qualities in different degrees according to the special requirements of various circumstances that the very different designs of the various types of boilers have been evolved.