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fall upon an object — probably it was, but he was not prepared to say it was 

 the best under all circumstances. He pointed out that when a ray of light 

 fell upon a surface of glass obliquely, a part of the light was reflected, and 

 if the eye were directed along the line of the reflected ray towards the 

 point of incidence, an image of the reflected body would be seen, not at this 

 point, bat apparently as much behind the reflecting surface as the reflected 

 body was in front of it. And if two divergent rays were reflected, it was 

 important to remember that their relation was not altered, but that they 

 would go on their reflected course as divergent rays still. And then, again, 

 it should be remembered that it was an axiom in optics that all rays which 

 proceeded from a point came back again to a point in the eye. When the 

 eye was looking in the position drawn on the board, so as to receive the re- 

 flected ray, the portion of the surface which reflected it was absolutely 

 invisible so far as the reflected light was concerned ; but then not all the 

 light would fall at that particular angle, some of it would spread out and 

 become diffused light upon the surface, and it was by this alone that 

 the surface could be perceived. The amount of light which was reflected 

 bore a proportion to that which was diffused, according to the angle at which 

 it fell, and the nature of the surface on which it fell. But the light which 

 became polarized was light which was directly reflected, and which, there- 

 fore, could not give an image of the surface of the object on which it fell, 

 teo that although he did not say this was not a good angle, he did not think 

 it was the only good angle for illumination. With regard to objects which 

 were not opaque, they could only be seen by light which was bent out of 

 its course in passing through them; and if an object having the same re- 

 fractive index as balsam were put into balsam, it would become at once in- 

 visible, for if the light passed through the object in a single bundle of rays 

 the same as it entered, it would not be possible to see the object. To be 

 seen it must emit rays from every one of its points, ar.d in viewing objects 

 through the microscope only the bundle of reflected or refracted rays 

 which went through the objective enabled the object to be seen, and no 

 others were of any use whatever in rendering it visible, no matter what the 

 angle might be at which they originally fell upon it. 



Mr. Ingpen said he did not know whether he had done the paper any in- 

 justice by not reading the whole of it, but there could be no doubt — looking 

 at the diagrams alone — that what he had stated was the tangible idea of the 

 piper, namely, that the light should fall upon the plane of the object at the 

 polarizing angle. The coutention was that the angle of polarization was the 

 angle at which an object should be illuminated, but the author did not say it 

 was the angle at which an opaque object should be examined. Of course it 

 was clear that they could in any case only view an object by the rays re- 

 flected from the surface in every direction. The contention appeared to him 

 to be that the direction of the rays of light reflected on or through the 

 object should bo always at the medium polarizing angle from the vertical 

 at which it was viewed. 



The President thought that until they had the whole of the paper before 

 them they could hardly discuss it further. He had great pleasure in pro- 

 posing a vote of thanks to the author of the paper. 



