ATOMS AND SUNBEAMS. 123 



araoDg the large aud ever-increasing circle of readers to whom the 

 great questions of physics are of interest. 



The division of matter into the three forms of solids, liquids, and 

 gases has acquired in these days a special signiticance now that the 

 constitution of matter is becoming in some degree understood. First 

 let it be noted that, though matter is capable of subdivision to a cer- 

 tain extent, yet that there is a limit beyond which subdivision could 

 not be carried. This statement touches uixin the ancient controversy 

 as to the infinite divisibility of matter. Even still we can find the 

 statement in some of our old text-books that there is no particle of mat- 

 ter so small that it could not be again subdivided into half. No doubt 

 (so far as most ordinary exi)enence goes) this statement may be unques- 

 tionable. It is quite true that we do not often reduce matter to frag- 

 ments so small tliat each of them shall be insusceptible of fui-ther con- 

 ceivable division, But, to illustrate the natural piiiiciplc now under 

 consideration, let us take tlie example of a body Avhich is itself com- 

 posed of but a single element. Think for instance of a diamond, 

 which is, as we all know, a jxtrtiou of crystallized caibou. It is true 

 that tlie reduction of diamonds to powder is a laborious process. Still, 

 diamond dust has to be produced in the finishing of the rough stone, 

 and this element will serve the purpose of our present argument better 

 than a substance of a composite nature. Each particle of the diamond 

 duv^t is, of course, as nuich a particle of carbon as was the original 

 crystal. We may however suppose that by a repetition of the process 

 a reduction of the diamond dust to powder still finer is accoini^lished. 

 The-grains thus obtained may have become so minute that they have 

 ceased to be visible to the unaided eye, and require a microscope to 

 render them i)erceptible ; but even after this comminution each of these 

 particles is still a veritable diamond. It possesses the properties, 

 optical, chemical, and mechanical, of the original gem, from which it 

 difters merely in the attribute of size. Even when the disintegration 

 lias been carried to such a point tliat each individual particle can be 

 only Just perceived by the keenest power of the most i^owerful micro- 

 scope, there is still no indication that the particles cease to possess 

 .the characteristics of the original body. 



These facts being undoubted, it was perhaps not unnatural to suppose 

 that the reduction could be carried on indefinitely, and that even if the 

 smallest fragment of diamond which could be seen in a powerful micro- 

 scope were reduced to a millionth i)art, and each of those to a million 

 more, yet that the ultimate particles thus reached would be diamonds 

 still. Now, however, we know that that is not the case. The smallest 

 liarticle visible under a microsco])e might indeed be crushed into a thou- 

 sand parts, and each one of those parts, though wholly inappreciable to 

 our sense of touch or vision, would nevertheless be a genuine diamond. 

 If however the subdivision be carried on until the particles produced 

 are, roughly speaking, one-millionth part of the bulk of the smallest 



