232 REPORT—1840., 
back to sulphurets ; and accordingly, in the neighbourhood of 
iron exposed in these conditions, organic matters are frequently 
found, lined, penetrated, or coated with crystals of bisulphuret 
of iron (Fe 8), or common pyrites, while their oxygen has gone 
to form carbonic acid and hydrosulphuric acid, both in their turn 
again to react in presence of air and water upon the iron. 
Hence, then, the prodigious power of degradation of castings 
or forgings of iron, when exposed to the foul water of the sewer- 
age of great cities, as so often observed; hence the cause of the 
destructive action of ‘‘bilge-water’’ upon the holding down 
bolts of marine engines. 
172. A very interesting case, verifying the occurrence of these 
phzenomena, has recently been observed and examined by the ac- 
curate Berthier*. ‘On the 15th June, 1837, an ancient malle- 
able iron anchor was taken up from the bottom of the river 
Seine, nearly opposite Gros Cailloux. It was found imbedded in 
a conglomerate of pebbles, bones and altered wood, with grains 
of sand and fragments of pottery, of a light gray colour, and 
held together by a calcareous cement, which had accreted round 
the metal. The anchor was two metres long, and weighed not 
less than 200 kilograms. It was thought to be of the fifteenth 
century ; its form, however, agrees with those of the sixteenth; 
and it cannot be more ancient than a.p. 1400. ‘The crust 
was easily detached by a blow. At one end was found a piece 
of wood in immediate contact with the iron; this had pre- 
served its ligneous texture, so as to be easily recognisable ; but 
it was deeply altered in its qualities. Its aspect was that of a 
dark gray homogeneous mass, with an uneven fracture, and it 
was strongly magnetic. By calcination and roasting, it lost 
0°375 of its weight, and exhaled a strong odour of sulphurous 
acid. Acetic acid dissolved from it 0°65 of pure carbonate of 
lime, while hydrochloric acid dissolved it nearly entirely with 
disengagement of hydrosulphuric acid. 
«The residue was composed of portions of unaltered wood, 
mixed with a small quantity of persulphuret of iron (bisul- 
phuret). 
“‘The analysis of the whole gave 
Carbonate lime . . che hake Tova 
FeS=protosulphuret iron. . . . 0°18 
FeS,=persulphuret'iron . . . . O07 
Ligneous patter Ae Yo OE Mt 0) et ee 
1°00 
* Annales des Mines, vol. xiii. p. 664. 
