104 J. Nicklés on a New Kind of Electro-magnet. 
V. This deposit probably belongs to the Pliocene, or Newer 
Tertiary. 
1. So far as we know, it lies immediately beneath the drift. 
2, It is destitute of any consolidated beds, save the nodules of 
hematite; which is not true of any of our miocene or eocene de- 
posits, 
3. The brown coal of continental Europe, to which ours cor 
responds closely in appearance, belongs to the newer tertiary. 
I confess that these arguments are not sufficient to remove all 
doubts from my mind as to the part of the tertiary group to 
which this formation should be referred. All geologists, however, 
I think, will say that it has marked peculiarities, which distin- 
guish it from all the tertiary deposits of our country hitherto de- 
scribed; and we may at least say, that the presumption is strong- 
ly in favor of its being pliocene. It is rather remarkable if it 
was an oceanic deposit, that no marine remains have been found 
in it. I believe, however, that this is very much the case 1 
Germany ; though, unfortunately, the papers of Horner, Von De- 
chan, and others, on the brown coal are not within my reach. 
Arr. XVIL—On a New Kind of Electro-magnet; by 
Jerome Nicxk.is. 
5 
In the beautiful researches on magnetism of MM. Lenz and 
Jacobi, these authors have admitted that the magnetism devel- 
oped in an electro-magnet does not depend on the length of the 
arms, but that this power is subordinate to the number of turns 
of the spiral which compose the helix.* 
The valuable report published by Professor Muller of Friburg, 
this opinion. M. Muller deduces from his experiments the for 
lowing conclusions: ‘Other things being equal, the length of the 
arms of 
raised.” 
M. Dub has arrived at a different opinion, from recent expert 
ments,t which have satisfied him that, under like circumstances, 
researches of M. Dub were published. ; 
I have pursued for this purpose two different methods, the 
details of which I will give in a future communication. One * 
pede Ea os cae ee 
* Poggendorff’s Annalen, Ix, p. 464. 
+ Berichte iiber die Fortschritte der Physik, 1 . 521. 
+ Poggendorff’s Annalen, lxxx, oe a ee aa 
—— — os —_ — 
a 
