Mr. Faraday on the Nature of Matter. 137 



used the word atom in their stead ; they did not express the 

 hypothesis as well as the fact. 



But it is always safe and philosophic to distinguish, as much 

 as is in our power, fact from theory; the experience of past ages 

 is sufficient to show us the wisdom of such a course ; and con- 

 sidering the constant tendency of the mind to rest on an as- 

 sumption, and, when it answers every present purpose, to forget 

 that it is an assumption, we ought to remember that it, in such 

 cases, becomes a prejudice, and inevitably interferes, more or 

 less, with a clear-sighted judgement. I cannot doubt but that 

 he who, as a mere philosopher, has most power of penetrating 

 the secrets of nature, and guessing by hypothesis at her mode 

 of working, will also be most careful, for his own safe progress 

 and that of others, to distinguish that knowledge which con- 

 sists of assumption, by which I mean theory and hypothesis, 

 from that which is the knowledge of facts and laws ; never 

 raising the former to the dignity or authority of the latter, nor 

 confusing the latter more than is inevitable with the former. 



Light and electricity are two great and searching investiga- 

 tors of the molecular structure of bodies, and it was whilst 

 considering the probable nature of conduction and insulation 

 in bodies not decomposable by the electricity to which they 

 were subject, and the relation of electricity to space contem- 

 plated as void of that which by the atomists is called matter, 

 that considerations something like those which follow were 

 presented to my mind. 



If the view of the constitution of matter already referred to 

 be assumed to be correct, and I may be allowed to speak of the 

 particles of matter and of the space between them (in water, or 

 in the vapour of water for instance) as two different things, then 

 space must be taken as the only continuous part, for the par- 

 ticles are considered as separated by space from each other. 

 Space will permeate all masses of matter in every direction 

 like a net, except that in place of meshes it will form cells, 

 isolating each atom from its neighbours, and itself only being 

 continuous. 



Then take the case of a piece of shell-lac, a non-conductor, 

 and it would appear at once from such a view of its atomic 

 constitution that space is an insulator, for if it were a con- 

 ductor the shell-lac could not insulate, whatever might be the 

 relation as to conducting power of its material atoms; the 

 space would be like a fine metallic web penetrating it in every 

 direction, just as we may imagine of a heap of siliceous sand 

 having all its pores filled with water; or as we may consider 

 of a stick of black wax, which, though it contains an infinity 

 of particles of conducting charcoal diffused through every 



