EHRENBERG ON ORGANIC MOLECULES AND ATOMS. 569 
have become rather too bold. Not content with regarding atoms as 
ideal unities, or as indefinitely small magnitudes, we have endeavoured 
to find for individual atoms or for certain minute groups of them an 
expression of a proximate finity, and even to fix its magnitude and to 
determine it by numbers. Indeed it appears that but little is wanting 
in our days to induce bold theorists to attack in good earnest the ma- 
terial primitive particles of bodies, to clutch them fast, and to build 
up with them even to organic structures, and thus to sport with them. 
Newton indeed thought he might assume the elementary particles of 
colours in bodies of a certain magnitude and perceptible to sense. He 
says, p. 64, Prop. vii., “ For if those instruments (microscopes) are or 
can be so far improved as with sufficient distinctness to represent ob- 
jects five or six hundred times bigger that at a foot distance they appear 
to our naked eye, I should hope that we might be able to discover some 
of the greatest of those corpuscles. And by one that would magnify 
three or four thousand times, perhaps they might all be discovered, 
but those which produce blackness.” If we now suppose that Newton 
had rightly estimated the natural acuteness of the vision of the human 
eye, his elementary particles for the red colour must not amount to less 
than 35355 of a line in diameter, as will be seen lower down; and 
between this magnitude and that of ,z,2o9 all the elements of colours 
except black would be found. It is however probable that Newton sup- 
posed the power of vision of the human eye to be less, and therefore 
the size of the elementary particles to be much greater. However 
we must here not forget, as Herschel has already remarked in his Optics, 
that Newton distinguished the elementary particles of colours from 
atoms, as later philosophers have also done, although he does not ex- 
press himself to that effect. In that passage Newton does not speak of 
atoms but of colouring particles. (JVewton’s Opticks (1704), book ii. 
‘part iii. Prop. vii. p. 64. 
The small magnitudes which have been employed for the explanation 
of the phenomena of light in the undulatory theory give a great defi- 
niteness to the calculation ; they can however only be regarded as 
hypothetical and not as real demonstrated magnitudes, as the whole 
theory, even though it possesses great probability, is in want of full 
confirmation. The smallest lengths of a wave of light which can be 
shown by an exact calculation, do not amount to more than the 554 aD 
of an inch, or about 3555 of a line. Now as the particles of ether 
must be considerably smaller than their undulations, there is in that 
number a limit, arbitrary indeed, but yet determinate, for its maximum, 
which gives an expression for its smallness. If from the impondera- 
bility of very great condensed masses of light or of ether we were to 
form a conclusion as to the smallness of the elementary corpuscles as 
ponderable objects, we should be obliged to place the limits of that 
maximum at a still much greater distance. All these however, even 
