repetition of M. Arago's experiments on magnetism, 475 
of iron present may have deceived us) a decisive result has 
been obtained ; and, what is very singular, this body is carbon, 
in that peculiar state in which its density, lustre, degree of 
hardness, and high conducting quality, both as regards heat 
and electricity, seem to give it some title to a place among 
the metals. This is the state in which it is precipitated by a 
red heat from coal-gas. It is found in thick masses encrust- 
ing the interior of the retorts, gradually blocking them up, 
and in time rendering them useless. It is composed of coats 
frequently curved round a centre, and exhibiting a radiated 
structure, but oftener in laminae of a fine close grain, a 
beautiful gray colour, and in some varieties of a shining me- 
tallic brilliancy, between that of plumbago and hardened 
steel ; some portions yield readily to the knife, but others of 
a darker hue and dull earthy fracture, resist obstinately, and 
give copious sparks with steel. The two sorts are found 
alternating or intermixed in the same specimen. The mag- 
netism developed in this singular substance is, however, too 
feeble to admit of precise measurement, and is only rendered 
barely sensible by delicate management. 
14. The second process alluded to as employed by us to 
compare the relative magnetic forces of the different bodies 
examined, consists in suspending magnetised bars over re- 
volving discs of them, and observing, not the point of equili- 
brium but the velocity generated, or the time required for 
the description of certain spaces ; in other words, by measur- 
ing not the statical, but the dynamical effect. These me- 
thods, for distinction's sake, may be called he statical and 
dynamical methods of observation. 
In the original experiment of M. Arago, a magnetic 
MDcccxxv. 3 Q 
