But these extravagances have had the good effect of giving us accurate measurements of nearly all the dimensions of the Great Pyramid, and raising a great deal of discussion as to its aim and origin. In the first place it is quite clear that its primary object was to provide a royal tomb. A tomb of solid masonry with a base larger than Lincoln's Inn Fields, and 130 feet higher than St. Paul's, seems very incomprehensible to modern ideas, but there can be no doubt as to the fact. When the interior is explored both of this and other pyramids, nothing is found but one or two small sepulchral chambers containing the stone coffins of a king or queen. The Great Pyramid is not an exceptional monument, but one of a series of some seventy pyramid-tombs of kings, beginning with earlier and continued by later dynasties of the Old Empire. The reason of their construction is obvious. It originates from the peculiar ideas, which have been already pointed out, of the existence of a Ka or shadowy double, and a still more ethereal soul or spirit, whose immortality depended on the preservation of a material basis in the form of a mummy or likeness of the deceased person, preferably no doubt by the preservation of the mummy. This led to the enormous outlay, not by kings only, but by private persons, on costly tombs, which, as Herodotus says, were considered to be their permanent habitations. With an absolute monarchy in which the divine right of kings was strained so far that the monarch was considered as an actual god, it was only natural that their tombs should far exceed those of their richest subjects, and that unusual care should be taken to prevent them from being desecrated in future ages by new and foreign dynasties. Suppose a great and powerful monarch to have an unusually long and prosperous reign, it is quite conceivable that he should wish to have a tomb which should not only surpass those of his predecessors, but any probable effort of his successors, and be an unique monument defying the attacks not only of future generations, but of time itself.