text:  After 1872 , steel started to be introduced as a material for construction . Compared to iron , steel allows for greater structural strength for a lower weight . The French Navy led the way with the use of steel in its fleet , starting with the <unk> , laid down in 1873 and launched in 1876 . <unk> nonetheless had wrought iron armor plate , and part of her exterior hull was iron rather than steel . 
  