156 



PRACTICAL TREATISE ON THE MICROSCOPE. 



like process connected with the disc of metal carrying the 

 chimneyj and by it both opaque and transparent objects can 

 be illuminated. 



For convenience of carriage, the tube, and the chimney, c, 

 can be removed, and the inner tube, d, having been pulled out 

 of b, the chimney, with a cylinder of card-board covered with 

 cloth, can be slid over the tube, b, and the whole wiU then pack 

 in a small compass. The cylinders of wax are similar to those 

 constructed by Molynettx, but the first mention of their 

 application as an illuminator for the microscope was made by 

 Mr. Jackson to the Microscopical Society in 1841. 



A wax candle will be found to give a very pure white light, 

 and may be used as a substitute for the lamp ; but unless the 

 flame be covered with a chimney, the constant flickering from 

 currents of air, occasioned by persons moving about in the 

 room, becomes an annoyance. The level of the flame is also 

 constantly varying as the candle is being consumed, hence it 

 is necessary to employ such a candlestick as that represented 

 by fig. 109 ; by means of which either a long or a short piece 

 of candle, c, may be brought to the re- 

 quired height by moving the socket into 

 which the candle fits, either up or down 

 the stem, b, that supports it, and fixing it 

 by a screw. A foot, a, loaded with lead, 

 win be required to keep the candlestick 

 perfectly steady. Many persons now 

 burn camphine ; the lamps, however, are 

 generally too high for the microscope; 

 but a small lamp, mounted on an ad- 

 justable stand, especially adapted for 

 the microscope will be hereafter de- 

 scribed. 



Those who may have their houses supplied with gas will find 

 that by means of a flexible tube connected with an argand or 

 other burner, mounted on a moveable stand, they will get a 

 very convenient light for all purposes. If, for instance, in 

 the centre of the room there be a chandelier, then a flexible 

 tube may be screwed to one of the pipes, and being attached 



Fig. 109. 



