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that the differential equations holding in such a system must be of 
a different form from Newron’s. On the other hand the system of 
Föprer does not require any alteration of Newron’s differential equations, 
but only a definite value of some integration constants (§ 2). 
c. The problems studied by Konkmuier') are in many respects 
more extensive. So he eliminates also absolute time. In this connection 
it is sufficient to state, that he does not find equations of the type 
of § 4, because he does not make use of Förrr’s hypothesis. 
d. Einsrei gives in his theory of relativity a way of relativating, 
founded on quite different principles from those held in this essay. 
This is connected with the fact that he wants to relativate not only 
mechanical but also electromagnetical and optical phenomena. 
e. In connection with an experiment, made by Förrr*) and a 
remark by Freunpuicu’), the following thought-experiment may be 
discussed: At the north-pole of the earth the pendulum-experiment 
of Fovcaurr is made. Under the pendulum a heavy flywheel with 
vertical axis of rotation has been mounted. Problem: Does the 
pendulum’s motion alter, when we revolve the flywheel? Förrr’s 
hypothesis and our equations give us the following answers: With 
respect to the principal system remains: 1°. the rotation of the 
pendulum’s plane permanently =0; 2°. the sum of moments of 
momentum of flywheel and earth = a constant, also this sum for 
the rest of the bodies of the universe, because the total sum has to 
remain —0Q. Consequently the rotation of the pendulum’s plane 
with respect to the rest of the bodies (the fixed stars) does not alter 
(it does alter with respect to the earth, the rotation of the latter 
having undergone some change). 
f. From the point of view of Newron’s mechanics can be said: 
1°. If only two celestial bodies were in universe, it were possible 
that they moved round each other at a constant distance. 2°. A 
liquid mass, supposed to be the only body in space, can be flattened 
by centrifugal forces, though no relative motion of its particles is 
observed. With the view taken here, which is based on Förrr’s 
hypothesis, this is impossible. 
g. For the transformations of $ 4 we can start from a principal 
') N. H. KorkMEYER. Eliminatie van de begrippen assenstelsel, lengte en 
tijd uit de vergelijkingen voor de planetenbewegingen. Dissertation Amster- 
dam 1915. 
*) A. Förrpr. Sitzungsber. der math.-phys. Klasse der Bayr. Ac. der Wiss. 
1904. Bd. 34, p. 3. 
5) ERWIN FREUNDLICH. Die Grundlagen der EiNsreiNschen Gravitations- 
theorie. Berlin 1916, p. 27, 
