3 1 4 D O C U M E N T 1 8 8 M A Y 1 9 2 8 The employment of total reflection was an after thought, and I fear I misunder- stood a statement of Lord Rayleigh,[3] from which I concluded that the object (Schicht S) could be brought as close as of a wave length from the quartz plate before the light came through from the plate generally, in the way you mention. There remains the possibility of a hole (ein winziges Loch)—One actually finds such holes, ready to hand, in pieces of badly silvered glass. A fragment from a cheap Thermos flask, for instance, contains countless small holes comparable in size with colloidal particles. No doubt they are due to the presence of colloidal par- ticles on the surface of the glass, at the time of silvering. Unfortunately the silver rubs off very easily, and would be difficult to keep clean. A better way would be, if one could construct a little cone or pyramid of quartz glass having its point P brought to a sharpness of order c.m. One could then coat the sides and point with some suitable metal (e.g. in a vacuum tube) and then remove the metal from the point, until P was just exposed. I do not think such a thing would be beyond the capacities of a clever experimentalist.[4] I know that needles can be made of quartz glass with exceedingly minute points, and there does not seem any reason why a point as sharp as c.m. might not be secured. If you should happen to know any experimental physicist who would care to try to utilise the idea in any form it is very much at his service. I have no pretensions to be a physicist myself, but when the idea occurred to me, it seemed to open up a prospect of penetrating into the submicroscopic region, and I read up whatever I could find on the subject, to see if I could put it into a practicable form. I feel sure that some idea of the kind will be made use of ultimately, but it obvi- ously requires to drop into the brain of an experimental genius. Why it came into mine I do not know, for I had hardly ever looked through a microscope in my life. With apologies for troubling you in the matter. Yours Very Truly E. H. Synge P.S. The following way of obtaining a glass point of dimensions c.m. has just occurred to me—but I do not know if it is practicable. A very small colloidal particle of iron enclosed in a glass bead, which is kept at a temperature at which the glass is plastic. A powerful electromagnet is placed very close to the glass bead—and draws the particle of iron to the surface of the bead. The force of the magnet on the particle then acts in opposition to the surface tension of the bead, and if the magnet is sufficiently powerful, a little excrescence should be formed on the bead, the size of the point of which should be comparable with the size of the particle.—The particle might be drawn out of the glass entirely,— the glass being cooled at the proper moment. 1 50 ----- - 10–6 10–6 10–6