346 



Note on Coloured Illumination. 

 By Julius Rheinbero. 



{Read December 18th, 1896.) 



I have the honour and pleasure of bringing before you this 

 evening a new form of substage differential colour illuminator 

 which I have designed in order to simplify and facilitate the 

 use of colour discs and other stops in the substage of the micro- 

 scope. 



You will see that it consists essentially of a box, or slide 

 carrier fitted under the condenser, in which there are a number 

 of metal slides which can be pulled out or pushed in quite 

 independently of one another by means of little handles on both 

 sides of the carrier. Each slide has two circular apertures, the 

 one being fitted with a colour disc or other stop, the other one 

 being left free. The kind of stop is indicated on the handle. 

 The openings in the slides are so arranged that when the 

 apparatus is closed all the free openings coincide, so that 

 illumination can be effected in the ordinary way. When any 

 other illumination is required it is only necessary to pull out 

 the particular stop, or combination of stops, each stop being in 

 accurate position when pulled out as far as it will go. 



In the apparatus I have here there are 19 stops, viz.. a dark 

 ground stop, four stops which cause the background to assume 

 various colours, four which cause the object to assume various 

 colours, stops causing the object to be illuminated in different 

 colours from opposite sides in various colours (for showing 

 striations), and one causing the object to be illuminated in 

 different colours at right angles to each other, fur showing 

 striations etc., similarly situated. There are also stops for 

 oblique light, several annuli, and a ground glass stop, making 

 a compendium no doubt somewhat too great for the general 

 worker, but which is very serviceable to the experimentalist. 



As far as colour discs arc concerned the stops are so arranged 

 that all those which can be pulled out from the loft side of the 



