VOL. XXX.] PHILOSOPHICAL TRANSACTIONS. 279 



that sometime before, and the first age of the empire, the humour of these 

 kinds of floorings much prevailed among the Romans: therefore it is no wonder 

 they are found in so many places of this island. But, in the time of Pliny, 

 (Hist. 1. 36, c. 25) they began to be out of use on the ground ; though still 

 made above stairs, or in chambers. Whether the lithostrota in chambers were 

 usual in Vitruvius's days, we have no warrant to suppose, from any hint in his 

 writings ; though he gives rules for making them, piano pede, on the ground, 

 and sub dio, (1. 7j c. J) (which from the method prescribed must be) aloft : be- 

 cause for sustaining those sub dio, he orders the work underneath to be well 

 secured, with two layers of plank across each other, and nailed down ; and 

 then the statuminatio or pitching, the mortar, terrace and tesserae, as before on 

 the ground. But because by sub dio Vitruvius could not mean chambers ; and 

 though Pliny informs us the Grecians used to cover or flat-roof their houses 

 with these pavements ; yet since neither Vitruvius nor Pliny mention any such 

 mode prevailing in their times at Rome ; it remains, that we may suppose sub 

 dio, or the subdialia of Vitruvius, to mean pavements mounted on pillars or 

 arches, which might afford delightful terraces out of the upper rooms, and 

 shady piazzas underneath : and in this sense perhaps may be understood the 

 portions pavimentata of Tully above-mentioned. 



By the many apartments, the foundations about these works point out, there 

 seems to have been nothing wherein the buildings that once stood there, might 

 come short of the magnificent structures, with which the Romans delighted to 

 gratify their luxury. The uses each were designed for cannot be determined, 

 nor whether there was a piazza covered with a lithostroton. But be that as it 

 may, it is next to demonstration, that there was some upper floor sustained by 

 wood,^ and paved with the tesserae, after the same manner as Vitruvius directs ; 

 and on the brick pavement, last discovered, the coat of ashes and wood coals 

 with nails, covered with large pieces of the rudus, and great lumps of the 

 tesserae well cemented together, and the nucleus adhering to them, show that 

 there was an upper pavement broken by its fall, when the fire had consumed its 

 support. 



As to the Roman architecture, it may not be amiss here to note ; that when 

 they designed a building, they could not immediately begin it : their prepara- 

 tions required time : by their well shaped durable bricks, and by their stone- 

 like mortar, we may plainly perceive, that they built not with such hasty mate- 

 rials as are now used. Vitruvius and Pliny both direct, that brick should be 

 formed in the spring, and be 2 years drying : and where Pliny speaks of their 

 mortar, he says, it was ordained by the old l^ws of Rome, that no builder 

 should build a house with mortar which had not been made 3 years before. We 



