2073. Curvilinear roofs. These roofs, an excellent specimen of which is shown in the large conservatory at Chiswick (fig. 605.), are by far the most ornamental, in an architectural point of view, but they have many serious inconveniences in practice. They are very difficult to heat, as the hot air rises to the roof and leaves the body comparatively cool, unless a great supply of fire heat be kept; and when heat is rapidly conducted away, and rapidly supplied by art, it is extremely difficult to obtain a sufficient degree of atmospheric moisture for healthy vegetation. It is also found that rays of light passing through lofty curvilinear glass roofs lose their influence on the plants, in proportion to the distance of the latter from the glass.