Letter from Frits Zernike to W Watsons and Sons Proposes to visit London to see CR Burch's results and to address the Royal Astronomical Society. Zernike has been experimenting with a 'phase contrast' microscope eyepiece. He requests advice on English patents and manufacturers and encloses a translation of a German patent specification (now catalogued as MM/18/47). It was for his work on the phase constant microscope that Zernike received the Nobel Prize for Physics in 1953. With accompanying note on the letter's provenance from Harold Horace Hopkins. 1934