eclipse of the sun of May 29, resulted in a striking
confirmation of the new theory of the universal attractive power
of gravitation developed by Albert Einstein, and thus reinforced
the conviction that the defining of this theory is one of the most
important steps ever taken in the domain of natural science. In
response to a request by the editor, I will attempt to contribute
something to its general appreciation in the following lines.

For centuries Newton's doctrine of the attraction of gravitation has
been the most prominent example of a theory of natural science. Through
the simplicity of its basic idea, an attraction between two bodies
proportionate to their mass and also proportionate to the square
of the distance; through the completeness with which it explained
so many of the peculiarities in the movement of the bodies making
up the solar system; and, finally, through its universal validity,
even in the case of the far-distant planetary systems, it compelled
the admiration of all.

But, while the skill of the mathematicians was devoted to making
more exact calculations of the consequences to which it led, no
real progress was made in the science of gravitation. It is true
that the inquiry was transferred to the field of physics, following
Cavendish's success in demonstrating the common attraction between
bodies with which laboratory work can be done, but it always was
evident that natural philosophy had no grip on the universal power
of attraction. While in electric effects an influence exercised
by the matter placed between bodies was speedily observed--the
starting-point of a new and fertile doctrine of electricity--in
the case of gravitation not a trace of an influence exercised by
intermediate matter could ever be discovered. It was, and remained,
inaccessible and unchangeable, without any connection, apparently,
with other phenomena of natural philosophy.

Einstein has put an end to this isolation; it is now well established
that gravitation affects not only matter, but also light. Thus
strengthened in the faith that his theory already has inspired,
we may assume with him that there is not a single physical or
chemical phenomenon--which does not feel, although very probably in
an unnoticeable degree, the influence of gravitation, and that, on the
other side, the attraction exercised by a body is limited in the first
place by the quantity of matter it contains and also, to some degree,
by motion and b