420 An Essay on the Refleclion, Refraction, and InJlecluM 



and in the paragraph No. 45, there is an attempt to prove that 

 bodies may seem to touch when they do not ; that is, they rest 

 suspended in the air without any support, and the following is 

 a transcript of so much of it as is necessary for my purpose. 

 " Mr. Melville, on examining the volubility and lustre of drops of 

 rain that lie on the leaves of colewort and some other vegetables, 

 found that the lustre of the drop is produced by the copious re- 

 flection of light from the flattened part of its surface contiguous 

 to the plant. He found also that when the drop rolls along a 

 part which has been wetted, it immediately loses all its lustre, 

 the green plant being then seen clearly through it; whereas in 

 the other case it is hardly to be discerned." 



Now it does not appear to me to be at all philosophical to sup- 

 pose that water, which is pulled towards the earth by the power 

 of gravity, could rest suspended in the air unless there was some- 

 thing intervening which prevented its descent ; and the more 

 so, as there is here evidently no dislike on the part of the plant 

 or the water to come in contact with each other, for when the 

 plant is dipped in water, water always adheres to it. It is surely 

 more reasonable to conclude^ that there is some substance ad- 

 hering to the surface of water which is siifficiently strong to resist 

 the pressure of the drop when it is small and let down gently*, 

 but which gives way when the drop, by an increase of quantity, 

 becomes more weighty, and also when it comes nearly in con- 

 tact with other water, because the attraction of the particles of 

 water to each other is stronger than the resistance of this fluid. 



But, whatever may be the cause of the separation, it only con- 

 cerns me to show that there is a substance adhering to the sur- 

 face of water, and that it is this substance and not the water that 

 has the property of reflecting light. Mr. Melville has shown 

 very clearly f that the drop reflected light while it was separated 

 from the leaf, but that it ceased to do so the moment they were 

 made to touch. Now, if it was the water that reflected this light 

 from the further surface, that surface would remain after the 

 drop had touched the leaf, and be still the same, and therefore it 

 ought still to reflect the same light as it did before : but if there 

 be such a substance as I have supposed between the drop and 

 the leaf when they are separated, that substance must necessarily 

 be removed when they -are brought into contact, or they never 

 could touch one another; and as light is only reflected from this 



* This phaenomenon is more common after dewfall than rain ; and this is 

 the cause of the brilliancy of the dew-drop, which so frequently seems to 

 embellish the language of the poets. 



■y The same phaenomenon is exhibited in drops of water sprinkled lightly 

 on dust, paper, und a gre^t many other bodies. 



surface 



