588 TRANSACTIONS OF THE 



and angle upon joint, with inclined junctions in every gradation 

 between the perpendicular and the horizontal, without coinciding 

 with either of them. 



In this obliquity you will detect the arch principles of con- 

 struction, that each stone either pressed or supported, with every 

 one of its sides, however numerous. This polygonal kind of 

 building is particularly applicable in, first, hydraulic works, as 

 it oifers nowhere a continuous joint to the water; second in forti- 

 fications; third, for railways in substruction and steep coverings, 

 and for large buildings and palaces. In these the walls would 

 be impervious to heat and moisture, as air would always be present 

 between the interstices in sufficient quantity to overcome both. 

 I would recommend the adoption of this method of building ac- 

 cordmg to determined and clearly defined principles and rules, 

 wherever the material for polygonal blocks is found. Our 

 government would do well, before they commence the construc- 

 tion of the intended post-office, courts, mint, &c., in this city, to 

 inform themselves with regard to this most imj)ortant matter. 



The Roman circus at Toulouse in France, and the very ancient 

 castle at Hastings in England, have endured for centuries, and 

 their walls are formed by building flints up in frames, and then 

 pouring cement into the interstices; they are supposed to be im- 

 pervious to heat and moistui-e. In Paris many external walls of 

 houses are constructed of framed timber, rubble and plaster; 

 thus, the frame timber structure being completed, strong oak 

 battan laths from two to three inches wide are nailed to the 

 quarters horizontally at three, five, or seven inches apart, accord- 

 ing to the character of the work, and the spaces between are 

 loosely built up with rough stone rubble; a strong mortar is then 

 laid on at both sides at the same moment, and pressed completely 

 through from the opposite sides at the same time, so that the 

 mortar meets and entirely embeds the stone rubble by filling up 

 all the hollows, and with so much body on the surface as to com- 

 pletely cover up and embed the timber and laths. This wall is 

 supposed in France to be impervious to heat and moisture. 



The ancients adopted several modes of constructing walls, in 

 which more or less masonry was used; they had verticular and 

 incertain walls; the verticular were esteemed the most beautiful, 

 the joints being so arranged, that, in all parts, the corners have 

 a regular position; whereas, in the incertain, the materials rest 

 irregularly upon each other. In most cases the wall should be 

 filled up with liquid mortar, called jointing. It consists in mix- 



