Dec. 7, r888.] 



SCIENTIFIC NEWS. 



57i 



by hydraulic presses,and collectively formed an apparatus 

 capable of moving masses of over 40c tons by a series 

 of successive efforts never exceeding 15 tons. 



in the arch itself. On April 25th a little lattice-work and 

 a few other parts not yet in position at the crown of the 

 arch were fixed, and the next day all was ready for in- 



Fig. 3. — Spring of the Arch. 



The completion of the intrados, or underside, of the 

 arch was effected on April 20th, 1884, and all the cables 

 were immediately slackened in case a fall of temperature 

 should produce excessive strains either in the cables or 



troducing the key of the extrados, or upper side, of the 

 arch. The hoisting of this key-piece was begun at 

 3 p.m., and at 7 p.m. it was in its place. With a lew- 

 blows from a hammer it gradually assumed its right 



