1900] MICROSCOPICAL JOURNAL 139 



foreign microscopes are beginniug to realize, and one by 

 one the English iraprorements are being adopted on the 

 Continent. It will be found that ordinary dayiight,though 

 perfectly suitable for low-power work, is unsuitable for 

 high-power and critical work, and as we are setting up our 

 microscope for critical work we will deal with lamp-light 

 illumination, accordingly. We need scarcely warn the be- 

 ginner that the use of direct sunlight is absolutely out of 

 the question for visual purposes. The lamp will be prob- 

 ably an ordinary half-inch paraffin lamp, with a shade,as 

 already described, but without a reflector, as this last only 

 succeeds in confusing the rays of light. Some workers 

 place the lamp on the immediate left of the instrument 

 in order to obviate any glare into the eyes, but the posi- 

 tion immediately opposite and in front has so many ad- 

 vantages in ease of manipulation that we prefer this po- 

 sition ourselves, and interpose a cardboard shade if re- 

 quired. The lamp will therefore be placed in the latter 

 position, with its wick turned edgeways forward, the light 

 being about 6 to 30 inches or thereabouts from the mir- 

 ror. It is well to accustom oneself to these approximate 

 distances, as high-power immersion-condensers are ad- 

 justed amongst other things for a definite distance of the 

 light from their back lenses. It will be necessary to care- 

 fully observe at the outset that the flame is immediately 

 opposite the centre of the stage, and that the tail-rod and 

 and the mirror are approximately truly in line with the 

 optic axis of the microscope. This is important. A slight 

 tilting of the mirror will then be sufficient to fill the tube 

 with light. For any objective lower than £ inch or finch 

 the condenser will not generally be required, and in this 

 case the concave mirror and the flat side of the flame can 

 be used. The concave mirror should be adjusted at such 

 a distance from the object on the stage that the rays of 

 light are approximately focussed on the latter. A little 

 reflection will show that when parallel, or nearly paral- 



