326 
MR. FARADAY ON THE FORMS AND STATES 
Fig. 16. 
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86. When sand is sprinkled uniformly over a plate on which large water 
crispations are produced, i. e. four, five or six in the inch, it gives some very 
important indications. It immediately becomes arranged under the water, and 
with a little method may be made to yield very regular forms. 
It is always removed from under the heaps, passing to the parts 
between them, and frequently producing therefore the accom- 
panying form, fig. 16, of great regularity. As the sand figure re- 
mains when the vibration has ceased, it allows of the determi- 
nation of position, the measurement of intervals, &c. very conveniently. 
8/. Very often the lines of sand are not continuous, but separated with ex- 
treme regularity into portions as represented fig. 1 7- The portions of these 
lines were sometimes, with little sand on the plate, very small, fig. 18; and 
when more sand was present they were thickened occasionally, fig. 19; then 
assuming the appearance of heaps arranged in straight lines at angles of 45° 
to the lines regulating the position of the water-heaps which formed them, 
and just double in number to the latter. At other times the sand instead of 
being deficient at the intersecting angle would accumulate there only, fig. 20 ; 
and at other times would accumulate there principally, but still show the 
original form by a few connecting particles, fig. 21. 
Fig. 18. 
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Fig. 19. 
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Fig. 20. 
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Fig. 21. 
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Fig. 22. 
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88. When the heaps were of the form described (84), the sand 
was still washed from under them ; it did not however assume j j 
lines parallel to the rectangular arrangement of the heaps, but -j — ^ —j 
was arranged as in fig. 22. ^ I, S 
89. When only the circular linear heaps (83) were produced, the sand 
assumed similar circular forms, concentric and alternating with the water 
elevations. 
90. On strewing a little lycopodium over the water for the purpose of 
gaining information relative to what occurred at the surface during the cris- 
