40 THE ART OF PROJECTING. 



surface of which is to be projected. Let fall, from a 

 height of two or three inches, a single drop of ether. 

 It assumes a characteristic form, will move about, but 

 will last only a few seconds, as it evaporates rapidly. 

 Rinse out the tank, and fill again with pure water, and 

 in like manner drop upon its surface any of the essen- 

 tial oils, of creosote, lavender, turpentine, sperm, and 

 colza oils. Each one will assume its peculiar form due 

 to cohesion. 



Fig. 29 represents the pattern exhibited by a single 

 drop of oil of coriander, and Fig. 30 the appearance 



Fig. 29. rio- 30. 



of oil of cinnamon. Some of these forms are very 

 beautiful, as, for instance, that due to oil of lavender. 

 This method of studying oils is used, by some experts, 

 to determine their kind and purity. These forms are 

 known as Tomlinson's Cohesion Figures. 



Again, into the same tank, well cleaned and filled with 

 water, drop a few small pieces of camphor-gum. As 

 soon as they touch the water they will begin to move 

 rapidly, dodging each other in a wonderful way, and ap- 

 pearing as if they were endowed with life. Their move- 

 ments will be accelerated if the water is warmed to a 

 hundred degrees, or a little more. 



