1 8 6 D O C U M E N T S 1 9 0 , 1 9 1 M A Y 1 9 2 8 190. To Hans Albert Einstein [Berlin,] 12 May 1928 Dear Albert, I am glad that you are coming, and that the Berger matter went so well.[1] Your letter was completely fine I added a few lines and sent it off. I can easily under- stand what you did, although I also think that, considered purely externally, you would have had more of a future there. The main thing is to be happy with one’s work and situation. I’m doing better, but still not exactly well. I’m still lying in bed and weak. In June I’ll probably go to Kissingen, where the devil is supposed to be driven out by the baths.[2] Then we’re going to the Baltic[3]—you just have to.[4] I want to see if we can sail by then. You can, for sure. If you come, we’ll rent a room in the neighborhood for you and your wife, because Margot[5] is there. Tell me when you arrive, then, and warm regards to you and your wife[6] from your Papa Szilard and I have applied for a patent on something very nice, namely, a heat in- sulation for refrigerators.[7] People use expensive sheets of cork. We use a few par- allel paper walls that are at a distance. At least the same insulation is achieved, without it costing hardly anything. 191. To Edward H. Synge [Berlin,] 14 May 1928 Dear Colleague, The decrease of the field outside the quartz platelet upon total reflection is not as steep as you indicate.[1] At grazing incidence, the field intensity decreases as[2] and refraction exponent of the quartz, y distance from the surface of the quartz, λ wavelength of the light. At a distance of a half wavelength, the intensity has de- creased to about one hundredth. One must, however, take into account that the ef- fective surface area of the sample is much larger than that of an ultramicroscopic particle, so that the brightening of the background by the sample will predominate over the light diffracted from the particle by a large factor, even at this short dis- tance. Furthermore, one should consider that it will be difficult to prepare a suffi- ciently smooth surface on the quartz platelet to prevent undesired scattering there. I thus believe that total reflection and scattering will make it practically impossible to obtain a small light source. This holds also in the case that the particle is embed- ded in the quartz or glass platelet. The other suggestions for obtaining a sufficiently