264 THE PRINCIPLES OF SCIENCE. 



expected to exhibit great apparent differences of conduct, 

 arising simply from the very various intensity of the forces 

 brought into play. Many persons have thought it requi- 

 site to imagine occult forces producing the suspension of 

 the clouds, and there have even been absurd theories 

 representing cloud particles as minute water-balloons 

 buoyed up by the warm air within them. But we have 

 only to take proper account of the enormous comparative 

 resistance which the air opposes to the fall of minute 

 particles, to see that all cloud particles are probably con- 

 stantly falling through the air, but so slowly that there 

 is no apparent effect. Mineral matter again is always 

 regarded as inert and incapable of spontaneous movement. 

 We are struck by astonishment on observing in a power- 

 ful microscope, that every kind of solid matter suspended 

 in extremely minute particles in pure water, acquires an 

 oscillatory movement, often so marked as to resemble 

 dancing or skipping. I conceive that this movement is 

 entirely due to the vast comparative intensity of chemical 

 actions when exerted upon minute particles, the effect 

 being 5000 or 10,000 greater in proportion to the mass 

 than in fragments of an inch diameter (vol. ii. p. 9). 



Much that was formerly obscure in the science of elec- 

 tricity, arose from the extreme differences of intensity 

 and quantity in which this form of energy manifests 

 itself. Between the instantaneous and brilliant discharge 

 of a thunder-cloud and the gentle continuous current pro- 

 duced by two pieces of metal and some dilute acid, there 

 was no apparent analogy whatever. It was therefore a 

 work of great importance when Faraday demonstrated 

 the identity of the forces in action, showing that common 

 frictional electricity would decompose water like that from 

 the voltaic battery. The relation of the phenomena be- 

 came plain when he succeeded in showing that it would 

 require 800,000 discharges of his large Ley den battery to 



