ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
521 
One of the chief advantages of this lamp is the facility with which 
the intensity of the light is graduated, an advantage which, coupled with 
the fact that it preserves the natural colours of pigments, renders it even 
superior to daylight. 
If this lamp is to be used in conjunction with an Abbe condenser, 
then instead of the curved glass rod a straight and very thick one is 
used. The outer end is adjusted about 9-10 cm. from the centre of the 
concave mirror, so that the light may fall on the very middle — a proce- 
dure much easier in practice than might be expected. 
Fig. 59. 
Sch 
In a further communication * Prof. P. Scliiefferdecker adds that the 
zircon cylinders have lately been rendered so much more durable that 
no cracking need be feared. It is advisable to use no more light than 
is absolutely necessary, otherwise the images are less well defined and 
the eye becomes fatigued. The glass rod should not be placed 
immediately beneath the diaphragm opening, but somewhat lower ; and 
this is especially necessary when delicate colourless objects are under 
examination. Finally, new tubing should not be used for conveying 
the gas, since the dust which it usually contains will have the effect of 
partially stopping up the burner. 
New Hot Stage and Accessories.! — Prof. W. Pfeffer describes a 
hot stage which keeps the temperature of the object and its environment 
* Central-Ztg. f. Optik u. Mechanik, xii. (1891) p. 137. 
f Zeitschr. f. Wiss. Mikr., vii. (1891) pp. 433-42 (4 figs.) 
2 O 
1891. 
