Polytechnic Association Proceedings. QQl 



tracery are also symbolic. While the upward tendency of all 

 the main lines of construction, are symbolic of the other great 

 doctrine of Christianity — the resurrection. The leading charac- 

 teristic of the Grecian style is the horizontal line — the beam sup- 

 ported by columns. 



Moldings are varied in both Grecian and Roman architecture. 

 Those in the former are generally irregular in their curves, and are 

 elliptical or parabolic. Whereas, those on Roman ai'chitecture are 

 arcs of a circle. • 



Turm'ng to mechanics, we find geometry at every point and in 

 every du'ection. The draftsman regards it as his especial science. 

 He is a regular dealer in lines, angles, and circles, and measm-es 

 them out in good measure, pressed down and shaken together. 

 His language becomes geometrical, his fingers move geometrically, 

 and he is, or should be, a geometrical thinker.. Enter a machine- 

 shop, and we find the artisan obtaining plane surfaces by the planer, 

 the chisel and the file; curved surfiicesby the lathe and the milling 

 machine; circles and cjdinders by the drill and borer. He can 

 point out octagonal brass boxes for journals; hexagonal nuts for 

 tightening up work; cylindrical pulleys; conical plugs; ball and 

 socket joints; levels for finding an horizontal line, and plumbs for 

 perpendicular ones. His very chisels are pyraniids; the ends of 

 his levers move in arcs of a circle, and all his work assumes geo 

 metrical figure and form. Adjom-ned. 



April 2, 1868. 



Professor S. D. Tillman in the chair. 



The Chairman gave, as usual, a summary of scientific progress. 

 The first item related to the carbonization of wood, from which it 

 appears that tDo high temperature generates tar and gaseous pro- 

 ducts, and diminishes in a corresponding degree the more useful 

 accessories. The experiments of Gillot show that wood, heated in 

 an oven to two hundred and sixteen degrees centigrade, yields about 

 two-thirds its weight of charcoal, and from seven to eight per cent 

 of acetic acid. A German improvement on the process of refining 

 sugar was alluded to, which consists in bringing the saccharine 

 juice — after having been clarified by lime and carbonic acid, in the 

 usual way — to the boiling temperature, and precipitating it with 

 [Inst.] 61 



