8 ON THE OLDER FORMS OF 



modelled after the terra-cotta tile, small bronze tiles in 

 Pliny's time, thin cleavages of slate, continuous sheet- 

 metal roofs and metal sheets modelled after the forms of 

 interlocking tiles. 



As to the relative merit of these various roof-coverings I 

 am not prepared to speak, nor is it with any intention of 

 urging the economic value of this material that this paper 

 is prepared ; it seems, however, that the terra-cotta tile 

 roof, when properly made is, all things considered, one of 

 the cheapest and most durable. It is certainly one of the 

 oldest and widest distributed. 



Definitions. — At this point it becomes necessary to de- 

 fine the difierent types of rooting-tiles now in use. Leav- 

 ing out of consideration all forms of interlocking tiles, and 

 recent modifications of the prevailing types now so well 

 known, we find among the older forms three distinct 

 types. 1 



The earliest form of roofing-tile known consists of two 

 elements, a wide tile (tegula) either square or rectangular, 

 more or less curved in section, and a narrow semi-cylin- 

 drical tile (imbrex) usually slightly tapering at one end to 

 fit into the wider opening of the one adjoining. The tegula 

 is placed on the roof, concave face upward, and the imbrex, 

 placed concave face downward, covers the lateral joint be- 

 tween two adjacent teguloe. I have not been able to learn 

 of any special English name for this tile ; in Grcrmany, it is 

 known as the hollow tile. From the fact that it is the earli- 

 est known tile, Graeber, in his exhaustive discussion of the 



^ It would be interesting to clear up the nomeuclature of rooflng-tiles as some 

 confusion exists through the same name being applied to diflereut forms of tiles, 

 thus tlie latest dictionary— "jTfte Center?/,"— almost encyclopaedic in its character, 

 gives under the definition of crown tile the English interpretation thus: "I. A flat 

 tile, a plain tile. II. A large bent tile or arched tile usually called a hip or ridge 

 tile, etc." These tiles are in reality two entirely different forms of tiles and neither 

 could be used for the purposes of the other. The synonymy would have to be 

 worked out by some student on the ground and versed iu the subject. 



