18.50. 



TIIK CIVIL EN(;iXEF,ll AND ARCH ITICCT'S JOURNAL. 



357 



\- E N 1' I I. A T 1 X c; A P P A R A T U S . 



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llil'lliilii!lllllli!!ii.l!!llill llllllllllll!i;l:::'a 



Fig. 2.— Section. 



