MEMORANDA. 



107 



Were sucli a solid made of glass, and placed below the 

 stage of the microscope, with its square side uppermost, rays 

 entering its curved surfaces in directions parallel to the axis 

 of the instrument would all be focalised into two lines, or 

 narrow spaces, intersecting each other at right angles. The 

 light would increase in intensity towards the centre of the 

 field. By stopping off a diagonal half of the square side I 

 think that a form of illumination would be obtained well 

 adapted for exhibiting at the same time the longitudinal and 

 transverse lines of PI. fasciola, Nav. rhomboides, &c. — 

 William Robertson, M.D., Edinburgh. 



Fiddian's Metallic Chimney. At the last meeting of the 

 Royal Microscopical Society Mr. C. Collins exhibited a 

 novelty in the way of a chimney, shade, and reflector com- 

 bined for the microscopist's lamp. The chimney is very 

 light, being made of thin copper, and without a seam, there- 

 fore not likely to open out or crack with any amount of heat 



COLLINS FIDDIAK METALLIC CHIMNEY. 



that may be applied ; the inside is coated over with a material 

 of intense whiteness. An aperture is left in one side, as 

 shown in the woodcut, for the insertion of a circular piece 

 which carries a thin glass, either plain or tinted, through 

 which the rays of liglit are emitted in one direction only. The 

 durability, and consequent economy of such a constructed 

 chimney, setting aside other qualities, is a recommendation 

 of no small importance. 



