I860.] Proceedings of the Asiatic Society. 425 



3. Below its support, in order to place a gnomon, make holes in 

 each side of the prism at the beginning of its length in such a man- 

 ner that they may not touch each other in the middle (of the prism). 



4. In order to conceal the gnomon (in this instrument) make 

 another hole near the support (of the prism) at its top in the middle. 

 Let the length of the gnomon be such as after placing it in the hole 

 (made in each side) the length of its external part be nearly equal to 

 the sixth part (of the length of the prism). 



5. A twelfth part of the length of the external portion of the 

 gnomon should be considered an Angula (a digit) in this Pratoda in- 

 strument. And find the sines of the (sun's) zenith distance and alti- 

 tude at the end of each of the given ghatikas (from the sun-rise of 

 every day, the number of the length of which is marked on the in- 

 strument) by the rule mentioned by former Astronomers. 



6. The sine of the (sun's) altitude (found at the end of the given 

 ghatikas from sun-rise) multiplied by 12 and divided by the sine of 

 the zenith distance (of the sun found at the same time) gives the 

 number of digits belonging to the given ghatikas. 



Thus find the digits belonging to the given gliatikas one, two, &c, 

 from sun-rise (of every day, the length of which is marked on the 

 instrument) and mark these digits on the respective sides (of the 

 prism) from the hole. 



7. (When you want to know the time after sun-rise at the given 

 day) place the gnomon in the hole of that side (of the prism) on 

 which the number of the gliatikas contained in the length of the 

 given day are marked, and hang the instrument by holding it in the 

 chain in such a manner that the shadow of the gnomon falls on the 

 side. And reckon the gliatikas (on the side) from the hole to the end 

 of the shadow. These gliatikas are after sun-rise (when you observe 

 the shadow) before noon, (but when you observe it) after noon they 

 are the gliatikas remaining (to complete the whole day.) (This 

 holds then when the end of the shadow falls exactly on the mark of 

 the ghatikas) but when it falls between two marks, there will be re- 

 quired a proportion." 



The Archdeacon then gave the following account of its character 

 and uses : — 



" The instrument appears to be roughly graduated and to be in a 



