OUJECTS.] INTRODUCTORY. 65 



46. The Structure of Water. 



We have seen that pure water is perfectly clear and 

 transparent. The naked eye can discern no differ- 

 ence between one part and another. In other words, 

 it has no visible texture or structure. It does not 

 follow that it really possesses none, however, for there 

 are many things which seem to be the same through- 

 out, or homogeneous, which yet show structure 

 if they are examined with a magnifying glass. Thus 

 the surface of a sheet of fine white paper looks per- 

 fectly even and smooth to the eye ; but a magnifying 

 glass of no great power will show the minute woody 

 fibres of which it is made up ; while, under a power- 

 ful microscope, the paper looks like a coarse matting. 



But if we put a small drop of water on a slide, such 

 as is used for microscopic objects, and cover it over 

 with a thin glass so as to spread it out into a film, 

 perhaps not more than TTr J TRr th of an inch thick, it 

 may be examined with the very -highest magnifying 

 powers we can command, and yet it looks as com- 

 pletely homogeneous and shows as little evidence of 

 being made up of separate parts as before. However, 

 this is still no proof that the water is not made up of 

 little parts, or particles, distinctly separated from one 

 another. It may merely mean that the particles are 

 so extremely small that they cannot be distinguished 

 even by microscopes which magnify four or five 

 thousand diameters. 



It is certain that solid bodies may be divided 

 into particles so minute that the best microscopes 

 show no trace of them. Common gum-mastic cannot 

 be dissolved by water, but it readily dissolves in 

 strong spirit or alcohol, and mastic varnish is an 



c 



