334 
MR. FARADAY ON THE FORMS AND STATES 
the square crispation. When this plate was vibrated, the mercury spread in 
all directions up the side, a natural consequence of the production of powerful 
oscillations at the middle, which would extend their force laterally, but quite 
against their being due to the opposition and crossing of waves originating at 
the sides. 
111. A limited depth of fluid is by no means necessary to produce crispa- 
tions on the surface (73). A circular glass basin about five inches in diameter 
and four inches deep was attached to a lath (69), filled with water and vibrated, 
the exciting rod being applied at the side (71). The surface of the water was 
immediately covered with the most regular crispations, i. e. heaps arranged 
quadrangularly. On taking out part of the water and filling it up with oil, 
the oil assumed the same superficies. On putting an inch in depth of mer- 
cury under the water, the mercury became crispated. The experiment was 
finally made with water fourteen inches in depth. Particles at a very moderate 
depth in the water seemed to have no motion except the general motion of the 
fluid, and the whole of the lower part of the water may be considered as per- 
forming the part of a solid mass upon which the superficial undulating portion 
reposed. In fact it matters not to the fluid, what is beneath, provided it has 
sufficient cohesion, is uniform in relation to the surface fluid, and can transmit 
the vibrations to it in an undisturbed manner *. 
112. The beautiful action thus produced at the limits of two immiscible 
fluids, differing in density or some other circumstances, by which the denser 
was enabled most readily to accommodate itself to rapid, regular and alternating 
displacements of its support when that support was horizontal, suggested an 
inquiry into the probable arrangement of the fluid when the displacements 
were lateral or even superficial. 
113. On arranging the long plate (67. 81) vertically, so that the 
lower extremity dipped about one third of an inch into water, fig. 27, 
and causing it to vibrate by applying the rod at X , or by tapping the 
plate with the finger, undulations of a peculiar character were observ- 
ed : those passing from the plate towards the sides of the basin were 
scarcely visible though the plate vibrated strongly, but in place of 
such appeared others, in the production of which the mechanical force 
* I have seen the water in a pail placed in a barrow, and that on the head of an upright cask in a 
brewer’s van passing over stones, exhibit these elevations. 
Fig. 27. 
