Of the two pipes that convey the water from the boiler, one crosses the building transversely--from the garden-front to the opposite side. Connected with this pipe, at certain distances, and in allotted numbers, are smaller pipes, five inches in diameter, laid horizontally, and immediately beneath the flooring of the building. These convey the water from the main pipe to certain required distances, and then bring it back to the _return_ main pipe, through which it flows into the boiler. The second main pipe conveys the water for heating the front of the building next to the Garden; and connected with this, as with the other main pipe, are smaller pipes through which the water ramifies, and then, in like manner, is returned to the boiler. Thus, then, by the mere propulsion of heat, a vast quantity of water is kept in constant motion throughout the Palace, continually flowing and returning, and giving out warmth that makes its way upwards, and disseminates a genial atmosphere in every part. To ensure pure circulation throughout the winter, ventilators have been introduced direct from the main building into each furnace, where the air, so brought, being consumed by the fire, the atmosphere in the Palace is continually renewed. [Illustration: REFERENCES A Egyptian Court B Greek Court C Roman Court D Alhambra Court E Assyrian Court F Byzantine Court G German Mediæval Court H English Mediæval Court I French Mediæval Court J Renaissance Court K Elizabethan Court L Italian Court M Italian Vestibule N Cort of Monuments of Art O Stationery Court P Birmingham Court Q Sheffield Court R Pompeian Court S Natural History T Natural History U Foreign Glass Manufactures V British Ceramic Manufactures W Ceramic Court X Fancy Manufactures Y Concert Room Z Screen of the Kings and Queens of England A A South Transept B B Great Central Transept C C North Transept Tropical Division D D Great Organ and Orchestra d d Concert Orchestra E E Saloon for Dining F F Dining Room f f Kitchens and Covered Way G G South Wing Dining Saloon H H The Terrace Dining Room J J Mammoth Tree K K The Great Water Towers L L The Library Reading Room M M Colossal Egyptian Figures N N Lecture Room _N.B. The numbers indicate those of the Flower Borders_ GROUND PLAN OF THE CRYSTAL PALACE.] PART II. THE INTERIOR.