EINSTEIN, ALBERT. Autograph letter signed (''Papa'') to Hans Albert, n.p., n.d. [postmarked Saranac Lake, N.Y., 2 September 1945], with a lengthy postscript by Maja Winteler-Einstein. 2 pages, 4to, 280 x 215 mm. (11 x 8½ in.), with original stamped and postmarked envelope.

EINSTEIN, ALBERT. Autograph letter signed ("Papa") to Hans Albert, n.p., n.d. [postmarked Saranac Lake, N.Y., 2 September 1945], with a lengthy postscript by Maja Winteler-Einstein. 2 pages, 4to, 280 x 215 mm. (11 x 8½ in.), with original stamped and postmarked envelope.

"MY SCIENTIFIC WORK HAS ONLY A VERY INDIRECT CONNECTION WITH THE ATOMIC BOMB"

A highly interesting letter written about a month after the first use of atomic weapons and the end of World War II. "My scientific work has only a very indirect connection with the atomic bomb. Indeed, I showed (39 years ago) that according to the special theory of relativity, there exists an equivalence between the mass and energy of a system, that is, that the two are only different manifestations of the same thing. Also I noted that the energies released by radioactive decay are great enough to be emitted in a nuclear reaction when there is an imbalance of mass."

Einstein writes about a model engine which Hans Albert has sent, with thoughts of obtaining a patent. Einstein cautions him about that plan, adding that "everything that has to do with the regulation of periodic phenomena has been worked on in the last century, that is, since the invention of the steam engine, and the internal combustion engine has been thoroughly explored for some decades. It is less a question of controlling the size of the valve than of making the stroke of the piston variable, in order to regulate the supply of fuel brought into the combustion chamber." In regard to his own work, he remarks "I have again made important progress and am entirely convinced that I have brought recent developments to the correct conclusion. However, I am probably too old to develop this to the point of comprehensible results. This does not diminish my satisfaction."