276 PHILOSOPHICAL TRANSACTIONS. [aNNO 1717. 



am inclined to take the meaning of Vitruvius, where he makes so plain a dis- 

 tinction between the tesserae and the sectilia ; that, the one was according to 

 the import of the name, formed by instruments out of stone, brick, and tile; 

 the other shaped in a mould and burnt. They were not of an equal size, none 

 exceeding an inch in length; the shortest were -^ of an inch: most of them 

 were equally made their whole length ; but of some the lower ends terminated 

 almost as sharp as a wedge, on purpose, as may be supposed, to be driven where 

 any interstices were left; at their heads likewise they were not all equal and 

 alike, some exactly square, some oblong square, some semi-lunar, but none 

 triangular; the diameter of those that were square was about -^ of an inch; 

 the longest side of those that were oblong at the head little exceeded half an 

 inch. The preparations for fixing this pavement here, go beyond those which 

 Vitruvius prescribes, in the firm wall near 6 feet below the surface, in the bed 

 of clay within it 2 feet thick, and in the foundation of brick under the clay. 

 But when we consider the situation of the ground here is low, not many feet 

 higher than the sea might be elevated at spring tides; and that it might either 

 be annoyed by land-springs after great rains, or by water oozing through the 

 earth from the sea so near; from which the work in time might receive damage, 

 we must allow the above-mentioned additions to be the result of a very judicious 

 foresight. 



The bath also was formed and secured by a very compact wall, of the same 

 breadth and depth with that on which the pavement rested ; the wall, which 

 sustained the north side of the pavement, formed the south side of the bath. 

 On this side, from the east end to the ends of the stairs, there was a solid seat, 

 12 feet 9 inches long, nearly 10 inches broad, and 14 inches high. The bottom 

 or floor of the bath was made after the same manner as the pavement, except- 

 ing the tesserae, and the thick bed of clay ; for under all, there was brick, then 

 a bed of the rudus or coarse mortar somewhat more than a foot thick, above that 

 the nucleus or terrace only, half a foot thick. The sides of the bath, the seat, 

 and the stairs, were plastered over with this terrace about half an inch thick ; 

 all which were throughout so hard, compact, and smooth, that when first 

 opened, the whole seemed as if it had been hewed out of one entire rock, and 

 polished. At the middle of the east end, at the bottom, there was a sink hole, 

 a little more than 3 inches long, and above 2 inches deep ; about 4 inches above 

 it there was another passage through the wall, of the same size; the first we 

 may suppose to let out the water which had been used, the other to let in fresh. 

 The stairs and seat were chiefly made of Roman brick, between 1 5 and 1 7 

 inches long, between 11 and 12 broad, and near one and a half thick. At the 

 north side of the bath the ground was not opened, but at the east end of the 



