322 
MR. FARADAY ON THE FORMS AND STATES 
is a certain quantity than when there is less. For small crispations, the water 
should flow upon the surface freely. Large crispations require more water 
than small ones. Too much water sometimes interferes with the beauty of the 
appearance, but the crispation is not incompatible with much fluid, for the 
depth may amount to eight, ten, or twelve inches (111), and is probably un- 
limited. 
74. These crispations are equally produced upon the under with the upper 
surface of vibrating plates. When the lower surface is moistened, and the bow 
applied (65), the drops which hang down by the force of gravity are rippled; 
but being immediately gathered up as described in the former paper (44), a 
certain definite layer is produced, which is beautifully rippled or crispated at 
the centres of vibration. 
75. Most fluids, if not all, may be used to produce these crispations, but 
some with particular advantages ; alcohol, oil of turpentine, white of egg*, ink, 
and milk produce them. White of egg, notwithstanding its viscosity, shows 
them readily and beautifully. Ink has great advantages, because, from its 
colour and opacity, the surface form is seen undisturbed by any reflection 
from the glass beneath ; its appearance in sunshine is exceedingly beautiful. 
When diluted ink is used for large crispations, upon tin plate or over white 
paper, or mercury, the different degrees of colour or translucency correspond- 
ing to different depths of the fluid, give important information relative to the 
true nature of the phenomena (78. 85. 97). Milk is, for its opacity, of similar 
advantage, especially when a light is placed beneath, and being more viscid 
than water is better for large arrangements (72. 98), because it produces less 
splashing. 
76. Oil does not show small crispations readily (120), and was supposed to 
be incapable of forming them, but when warmed (by which its liquidity is in- 
creased) it produces them freely. Cold oil will also produce large crispations, 
and for very large ones would probably be better than water, because of its 
cohesion. The difference between oil and white of egg is remarkable ; for the 
latter, from common observation, would appear to be a thicker fluid than oil : 
but the qualities of cohesion differ in the two, the apparent thickness of white 
of egg depending upon an elastic power (probably due to an approach to 
* Wheatstone. 
