338 On the Forms and States of Fluids [1831. 



pressure given by the exciting moist fingers is varied; with 

 each change of this kind an immediate change of the crispation 

 is observed. 



72. This form of apparatus was enlarged until a board 

 eighteen feet long was used, the layer of water being now three- 

 fourths of an inch in depth and twenty-eight inches by twenty 

 inches in extent. The sides of the cistern were very much in- 

 clined, so that the water should gradually diminish in depth, 

 and thus reflected waves be prevented. The vibrations were 

 so slow as to be produced by the direct application of the hand, 

 and the heaps were each from an inch to two inches in extent. 

 Though of this magnitude, they were identical in their nature 

 with those forming crispations on so small a scale as to appear 

 merely like a dullness on the surface of the water. 



73. In these experiments the proportion of water requires a 

 general adjustment, the crispations being produced more readily 

 and beautifully when there 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 unlimited. 



74. These crispations are equally produced upon either the 

 under or 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 im- 

 mediately 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 reflexion from the glass beneath ; its appearance in sun- 

 shine is exceedingly beautiful. When diluted ink is used for 

 large crispations, upon tin plate or over white paper, or mer- 



* Wheatstone. 



