302 Dr. Schafhaeutl on the Different Species of 
duum of the Swedish iron will assume the same appearance as 
the English, and so in the reverse case; this circumstance ex- 
plains why anchors made of English iron, although tougher 
than those made of Swedish iron, are almost twice as soon 
destroyed by the action of sea water. 
The same rule holds good, when iron, with other chemical 
agents, is treated in the dry way. For instance, at the same 
degrees of heat as those in which malleable iron of the specific 
gravity 7*4< has combined with the greatest quantity of carbon 
necessary for it to become liquid, — at the same degree of tem- 
perature Swedish iron of the specific gravity 7*7 (called Hoop 
L), or 7*8 (called double bullet), just begins to crystallize, 
forming steel, and sinking down to a specific gravity of 7*5. 
The quantity of the residuums of iron of the same descrip- 
tion bears a very remarkable relation to the specific gravity of 
the acid, as is evinced by the following table, showing the dif- 
ferent quantity of residuums of 35 grains of Welsh iron from 
the Maesteg iron-works, specific gravity 7*407. 
Specific gravity Residuum. Sulphuret of Lead, 
of the acid. 
1*160 . . . 6*770 .... 1*73 
1*140 . . . 9-244 .... 1*71 
1-103 . . . 13*711 .... 1*703. 
Mottled iron from the forges at Alais, departement du Gard, 
in the south of France : 
Specific gravity of Residuum. Sulphuret of Lead, 
the acid. 
1-16 .... 7*51 .... 6-06 
Acid very much diluted 1T42 . . . . 0*6475 
Acids still further diluted 21*49 . . . . T015 
In the fourth example I poured water over the fragments 
of iron in a retort, the beak of which was connected with two 
bottles of a solution of nitrate of lead, and 1 dropped only in- 
to the retort so much hydrochloric acid as to cause a very 
moderate evolution of hydrogen. In the last sample I put 
only a few drops of acid into the retort, just sufficient to cause 
a very slight attack of the iron. The third column of all the 
samples contains the quantity of sulphuret of lead obtained. 
The evolution of gas continued for several days, and when it 
ceased, the addition of acid had no further visible effect*. 
* As I repeated the last experiment but one, I put some fragments of the 
cast iron in the upper part of the beak of a new retort in order to witness 
the effect of the evolving gas on iron fragments. The next day I found 
the fragments converted into a black crumbly and rather unctuous mass, 
soaked with a yellowish liquid, which fastened it to the glass. On nearer 
