"Thus saith the Lord, the God of David thy father, I have heard thy prayer, I have seen thy tears: behold, I will heal thee: on the third day thou shalt go up unto the house of the Lord. And I will add unto thy days fifteen years; and I will deliver thee and this city out of the hand of the king of Assyria; and I will defend this city for Mine own sake, and for My servant David's sake. And Isaiah said, Take a lump of figs. And they took and laid it on the boil, and he recovered. And Hezekiah said unto Isaiah, What shall be the sign that the Lord will heal me, and that I shall go up into the house of the Lord the third day? And Isaiah said, This sign shalt thou have of the Lord, that the Lord will do the thing that He hath spoken: shall the shadow go forward ten degrees, or go back ten degrees? And Hezekiah answered, It is a light thing for the shadow to go down ten degrees: nay, but let the shadow return backward ten degrees. And Isaiah the prophet cried unto the Lord: and He brought the shadow ten degrees backward, by which it had gone down in the dial of Ahaz." The narrative in the Book of Isaiah gives the concluding words in the form-- "So the sun returned ten degrees, by which degrees it was gone down." The narrative is complete as a record of the healing of king Hezekiah and of the sign given to him to assure him that he should recover; complete for all the ordinary purposes of a narrative, and for readers in general. But for any purpose of astronomical analysis the narrative is deficient, and it must be frankly confessed that it does not lie within the power of astronomy to make any use of it. It has been generally assumed that it was an actual sundial upon which this sign was seen. We do not know how far back the art of dialling goes. The simplest form of dial is an obelisk on a flat pavement, but it has the very important drawback that the graduation is different for different times of the year. In a properly constructed dial the edge of the style casting the shadow should be made parallel to the axis of the earth. Consequently a dial for one latitude is not available without alteration when transferred to another latitude. Some fine types of dials on a large scale exist in the observatories built by Jai Singh. The first of these--that at Delhi--was probably completed about 1710 A.D. They are, therefore, quite modern, but afford good illustrations of the type of structure which we can readily conceive of as having been built in what has been termed the Stone Age of astronomy. The principal of these buildings, the Samrat Yantra, is a long staircase in the meridian leading up to nothing, the shadow falling on to a great semicircular arc which it crosses. The slope of the staircase is, of course, parallel to the earth's axis.