MOLECULAR MAGNITUDES. 657 



An instructive experiment may be made : First, finely pulverize 

 indigo, charcoal, or carmine, and then mix either of them with water, 

 and place under the microscojje, when an incessant movement of the 

 small granular particles will become apparent; and the smaller the 

 particles, the moi*e rapid and uniform will be their movements. These 

 movements are chiefly of a vibratory kind ; and it is when the par- 

 ticles are minutely divided, so as to approach the limits of microscopic 

 range, that this vibratory motion, together with an irregular axial 

 rotation, approaches a degree of perfection that is beautiful as well as 

 suggestive. This experiment is well calculated to assist us in forming 

 a mental conception of the magnitudes and the motions of those atoms 

 and molecules which have for their realm the regions below and be- 

 yond the immeasurably small. 



As to the shape and internal structure of atoms, there is no definite 

 knowledge ; but Helmholtz's studies of certain equations in hydro-ki- 

 netics, several years ago, gave rise to the idea that vortex-motion in 

 a frictionless medium .would exist forever an assumption which is 

 purely hypothetical ; but since the proposition has been enlarged upon 

 by Sir William Thomson who conjectures that the atoms might be 

 filaments or rings endowed with a vortex-motion the subject assumes 

 a shape better calculated to form the basis of a scientific theory. To 

 be sure, mathematical formulas might show that the behavior of a 

 vortex-filament in a non-resisting medium would answer to that 

 ascribed to atoms indestructible and unaltei-able through all time ; 

 still, at the same time, the means at hand for its complete mathemati- 

 cal verification are not adequate to place the subject beyond the 

 regions of theory. Prof. Tait, in a review of this subject in his 

 *' Recent Advances of the Physical Sciences," remarks that, " with a 

 little further development, it may be said to have passed its first trial, 

 and, being admitted as a possibility, may be left to time and the 

 mathematicians to settle whether it will really account for everything 

 experimentally found." 



Small as these atoms are, we are not permitted to stop here, but 

 remember that there is a finer medium environing them all, embracing 

 possibly a complexity of internal structure sufiicient to baffle human 

 investigation for all time. This cosmic or luminiferous ether is sup- 

 posed to fill all space, intermolecular and interstellar, and to be the 

 medium in which the atoms and molecules move like motes in the 

 sunbeam. 



Atoms and molecules may vibrate to and fro, or may execute vari- 

 ous oscillations about each other, with a moderate velocity, or perform 

 their motions with a rapidity beyond conception ; and be the intensity 

 of the vibrations ever so great or ever so small, these same vibi-ationa 

 determine the amplitude of the ethereal waves those waves of great- 

 est length giving rise to all the phenomena of radiant heat, while shorter 

 ones constitute light in all its luminous and chromatic efiects ; as also 

 VOL. XI. 42 



