NATURAL PHILOSOPHY, 187 



converted into a certainty in 1837, when Colonel Vyse discovered two of the 

 casing-stones, actually in situ, nearly in the centre of the northern face of 

 the pyramid. The angle at which these casing-stones are inclined (51 GO') 

 and the length of the base (764 feet) being both known, the total height of 

 the pyramid is easily ascertained, and all its dimensions are then satisfac- 

 torily determined. They are as follows: 



Feet. Inches. 

 Length of former base, including casing-stones, . 764 



Length of present base, 746 



Former height, including casing-stones, . . . 480 9 



Present height, perpendicular, 450 9 



Former height, inclined, 611 



Present height, inclined, 568 3 



Width of pavement in front of casing-stones in centre 



of northern side, 33 6 



Thickness of paving-stones, 19 



Acres. Roods. Poles. 



Former extent of base, 13 1 22 



Present extent of base, 12 3 3 



The angle of the casing-stones being 51 50', and the base 764 feet, the 

 height of the pyramid, supposing it to end in a point, would be 486 feet. 

 "What reason," asks Mr. Taylor, "can be assigned for the founders of the 

 Great Pyramid giving it this precise angle, and not rather making each face 

 an equilateral triangle ? The only one we can suggest is, that they knew the 

 earth to be a sphere; that they had measured off a portion ot one of its 

 great circles, and, by observing the motion of the heavenly bodies over the 

 earth's surface, had ascertained its circumference, and were now desirous of 

 leaving behind them a record of that circumference as correct and imperish- 

 able as it was possible for them to construct. They assumed the earth to 

 be a perfect sphere, and as they knew that the radius of a circle must bear a 

 certain proportion to its circumference, they then built a pyramid of such a 

 height, in proportion to its base, that its perpendicular would be equal to the 

 radius of a circle equal in circumference to the perimeter of the base. How 

 the thought occurred to them we cannot tell; but a more proper monument 

 for this purpose could not have been devised than a vast pyramid with a 

 square base, the vertical height of which pyramid should be the radius of 

 a sphere in its circumference equal to the perimeter of the base. It was 

 impossible to build a hemisphere of so large a size. In the form of a pyra- 

 mid all these truths might be declared which they had taken so much pains 

 to learn; and in that form the structure would be less liable to injury from 

 time, neglect, or wantonness, than in any other." 



Now, the exact angle which must be given to the face of a pyramid, in 

 order to enable it to fulfil these conditions, is 51 5V 14 //r ; to which the 

 observed angle of 51 5(K is as near an approach as the magnitude of the 

 work would probably allow. As a further proof that this coincidence in the 

 angles was not accidental, Mr. Taylor refers to the statement of Herodotus, 

 which he gathered from the official guardians of the pyramid at the time of 

 his visit, that "each face of the pyramid is eight plethra, and the height is 

 equal." He concludes that this measurement refers, not to linear but to 

 square measure; and that the statement signifies that the number of square 

 feet in each face of the pyramid is equal to the square of the height. Now, 



