[Illustration: 123. Restored Elevation of the Black Pagoda at Ranaruc. (From a Drawing by the Author.) No scale.] Whatever its origin, this amalaka is generally surmounted by a flat dome of reverse curvature, in the centre of which stands the kullus, or pinnacle, in the form of a vase, generally of very beautiful and graceful design. [Illustration: 124. Diagram Plan and Section of the Black Pagoda at Kanaruc, designed to explain the construction of Hindu Temples.] The great and at first sight puzzling question is, from what original is this curious combination of forms derived? It is like nothing found anywhere out of India, and like no utilitarian form in India that we now know of. It cannot be derived from the dome-like forms of the topes. They are circular both in plan and elevation. The sikras are straight-lined in plan, and their section is never a segment of a circle; it is not derived from any many-storeyed buildings, as the sikras or vimanas of the Dravidian architecture of the south of India, which seem certainly to have been copied from the many-storeyed viharas of the Buddhists, and we cannot fancy any class of domestic building which could have formed a model out of which they could have been elaborated. One curious thing we do know, which is that all the ancients roofs in India, whether represented in the bas-reliefs or copied in the caves, were invariably curvilinear--generally circular or rather ogee--having a ridge added externally to throw off the rain from that weakest part; but nothing on any bas-relief or painting gives us a hint of any building like these sikras. Another curious and perplexing circumstance regarding the sikras is that when we first meet them, at Bhuvaneswar for instance, or the Bay of Bengal, or at Pittadkul in the 7th century, on the west coast of India, the style is complete and settled in all its parts. There was no hesitation then, nor has there been any since. During the twelve or thirteen centuries that have elapsed since the erection of these earliest known examples, they have gone on becoming more and more attenuated, till they are almost as pointed as Gothic spires, and their degree of attenuation is no bad test of their age; but they never changed in any essential feature of the design. All the parts found in the oldest examples are retained in the most recent, and are easily recognisable in the buildings of the present century.