Letters from Louis Napoleon George Filon and others Consists of letters from : <li>Louis Napoleon George Filon concerning Pearson's inclined lens problem and providing results from A C Stevenson (2 letters).</li> <li>A C Stevenson discussing work by Dennis Taylor and the dislocation of the eye lens (2 letters).</li> <li>C H Usher regarding lenticular astigmatism, and constructive criticism of article (3 letters).</li> 1927