THE CONSTITUTION OF MATTER. 3 
We now know that matter is not indefinitely divisible, 
and that the smallest parts of the various simple substances 
existing in those that are naturally compound have not all 
the same dimensions, nor equal weights. Chemistry, by a 
course of analyses and measurements, has succeeded in de- 
termining the weights of atoms of the different elements, 
that is to say, taking as a unit an atom of the lightest ele- 
ment, hydrogen, in determining the weight of the atoms 
which are equivalent to this conventional unit in the various 
combinations. Though many savants continue to maintain 
that atomic weights are nothing but relations, and that 
the existence of atoms is a mere logical device, it seems 
more reasonable to admit, with the majority of those who 
have studied this difficult problem closely, that these atoms 
are actual realities, while it may be very far from easy to 
settle precisely their absolute dimensions. In any case, we 
may affirm that these dimensions are very much less than 
those presented by the particles of matter subjected to the 
most powerful and subtile methods of division, or decom- 
posed by the imagination into its minutest elements. ‘“ Let 
man,” says Pascal, “ investigate the smallest things of all 
he knows; let this dot of an insect, for stance, exhibit to 
him in its diminutive body parts incomparably more dimin- 
utive, jointed limbs, veins in those limbs, blood in those 
veins, in that blood humors, and drops within those humors 
—let him, still subdividing these finest points, exhaust his 
power of conception, and let the minutest object his fancy 
can shape be that one of which we are now speaking—he 
may, perhaps, suppose that to be the extreme of minute- 
ness in Nature. I will make him discover yet a new abyss 
within it. I will draw for him not merely the visible uni- 
verse but all besides that his imagination can grasp, the 
immensity of Nature, within the confines of that impercep- 
tible atom.” In this Pascal displays a feeling as true as it 
is deep of the infinitely small, and it is interesting to ob- 
