I. CG. Russell—Triassie Trap Sheets of New Jersey. 277 
vibrating systems, each ruled more or less by the motions of its 
own superposed magnet; to witness the deformations and 
decompositions of one molecular arrangement by the vibrations. 
of a neighboring group, to note the changes in form which take 
place when a larger magnet enters the combination, and to see 
the deformation of groups produced by the side action of a 
magnet placed near the bowl. 
n the vertical lantern these exhibitions are suggestive of 
much thought to the student. Of course they are merely sug- 
as to the grouping and mutual actions of molecules in space. 
1 will here add that I use needles floating vertically and 
horizontally in water as delicate and mobile indicators of mag- 
netic actions; such as the determination of the position of the 
oles in magnets, and the displacement of the lines of magnetic 
orce during inductive action on plates of metal, at rest and in 
motion. 
The vibratory motions in the lines of force in the Bell-tele- 
phone have been studied from the motions of a needle (float- 
ing vertically under the pole of the magnet), caused by moving 
to and fro through determined distances, the thin iron plate in 
front of this magnet. These experiments are worth repeating 
by those who desire clearer conceptions of the manner of action 
of that remarkable instrument. 
Art, XLL—On the Intrusive Nature of the Triassic Trap Sheets 
of New Jersey; by I. CO: RUSSELL. 
ALTHOUGH the trap sheets which traverse the Triassic rocks 
of New Jersey and of the Connecticut Valley are commonly 
spoken of as being dikes of igneous rocks, yet the proof of 
tary rocks, is very positively shown. 
The rid nee See Jase have a general north and 
south direction, usually conformable with the strike of the 
associa sa 
of the Triassic formation. The trap rocks, also, seem neually 
to be conformable in dip with the stratified rocks above and 
below them. ‘These facts, together with the consideration of 
