---Niels Bohr
Atomic theory and mechanics,
Nature,
Vol. 116, 1925, p. 852.
This article arose out of an address that Niels Bohr delivered,
on 30 August 1925, to the sixth Scandinavian Mathematical Congress in Copenhagen.
The quote is used an an epigraph on p. 276 in Operator Commutation Relations
by Palle E. T. Jorgensen and Robert T. Moore, D. Reidel, Dordrecht / Boston / Lancaster, 1984.
This quote from Niels Bohr is also reproduced in vol. 3 of
The Historical Development of Quantum Theory, Vol. 3:
The Formulation of Matrix Mechanics and Its Modifications, 1925-1926
by Jagdish Mehra and Helmut Rechenberg,
Springer-Verlag, New York, 1982,
the volume about Max Born and his times.
The quote is on the first page of the
Introduction, i.e., page 3 in vol. 3 of the Mehra-Rechenberg work. This even
constitutes the opening sentences of the Introduction, Mehra describing how
Bohr saw the developments from 1925 on as a revival of the long-established
connection between mathematics and physical theory.
The Bohr quote is from a Scandinavian conference, which is
carefully referenced by Mehra and Rechenberg. They also relied on recorded
conversations, and on the Bohr archives.
Some interesting links for Niels Bohr:
Bohr_Niels
[in the
MacTutor History of Mathematics archive
at the University of St Andrews]
Niels Bohr Archive