200 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



71. Again, the granite columns give the following height of the 

 incrustation : — 



ft. in. 



From No. 25 7 3 



From No. 26 7 7 



From No. 27 7 2 



Mean height 7 4 



Add height of base 1 4 



Height of great incrustation . . 8 8 



These columns therefore could not have stood in the central ele- 

 vated part of the area of the temple, because in that case the incrus- 

 tation must then have been 3 feet 7 inches lower down on them. 



72. If we compare in the same way the two portions of the columns 

 of African breccia, we find — 



ft. in. 



No. 16, height of top incrustation 3 9 



No. 18, height of top incrustation 2 8 



Now the difference of 1 foot 1 inch in the height of the water- 

 line is too large to attribute to any uncertainty in the measures, and 

 leads me to believe that I must have entered in my note-book by 

 mistake the word ' top ' instead of 'bottom ' of incrustation, when re- 

 cording the fragment described in No. 18. If this were the case, then, 

 adding the breadth of the incrustation which is 1 foot, we have for 

 the top of it 3 feet 8 inches, which I shall adopt. 



ft. in. 



Hence No. 16, height of incrustation. 3 9 



No. 18, height of incrustation 3 8 



Mean height 3 8j 



Height of base 1 4 



Height of elevated central part of the temple. . 3 7 



8~~7i 



which again is nearly the height of the top of the incrustation. It 

 is however known that the columns of African breccia were part of 

 the central temple. 



73. There is, however, one circumstance which requires an ex- 

 planation. The fragment described in par. 7 is covered with a 

 calcareous deposit of the same nature as that which we are con- 

 sidering. It is the middle portion of a large Cipolino column, of 

 which No. 8 is the base and No. 6 the top. 



Now since the middle portion must have fallen into the lake formed 

 by the hot spring (for it is incrusted all over), it is natural to inquire, 

 why the top portion has escaped that fate, and is found perforated 

 in all directions by the Modiolse ? The solution of this difficulty 

 seems to be, that the top portion of the column fell on a part of the 

 filling up of the temple w^hich was above the reach of the lake formed 

 by the hot spring, whilst the middle portion fell nearer the base of 

 the column and into the lake ; consequently, when the lake w^as filled 



