ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
235 
introduction of a stream of oxygen into a spirit flame, is not to bo 
recommended owing to its dangerous nature. The most perfect burning 
material is of course hydrogen, which can be easily transported in a 
compressed state in steel cylinders. In the Meckel oxy-hydrogen safety 
burner the light is produced by a plate of lime which emits 500 candles. 
The use of hydrogen is somewhat expensive and, unless every precaution 
is taken that it is quite pure, may be attended with danger. As a 
substitute for hydrogen where coal gas is not to be obtained, the benzine 
blowpipe burner shown in fig. 37 may be used. The vessel A contains 
pure benzine which is conducted along the tube L to the heating 
chamber H. The latter is heated by a small amount of spirit burning 
in the dish W, so that the benzine is volatilised. The vapour is ignited 
at the mouth of the blowpipe M. A small amount of vapour passes 
back through the tube Y, and keeps the chamber H hot. Oxygen is 
introduced by the tube K, and the flame is made to impinge upon the 
lime K. The small wheel B and the stop-cock B serve to regulate the 
flow of benzine. This burner gives a light of 200 candles, and is 
strongly [recommended by the author as quite free from danger and 
convenient in use. Pictures 3 m. in diam. can be obtained with it, 
which are clearly visible to an audience of 800 people. 
Wolff’s Hygienic Lamp-shade.* — Herr J. Bodenstock recommends 
the Wolff lamp-shade to all who are compelled to work by artificial light. 
There does not appear to be any very notable peculiarity in its con- 
struction. As seen in the figure it serves to protect the head of the 
observer from the light and heat of the lamp, while it reflects a strong 
light upon the work-table. At the same time, since the shade only 
covers part of the lamp, the room is not darkened. 
Marking Apparatus for Indicating the Position of Objects or 
Parts of Objects in Microscopical Preparations.! — Prof. S. H. Gage 
makes use as object-finder of a modified form of the apparatus devised 
by Dr. May of Philadelphia, and later by Winckel of Gottingen. By 
means of this apparatus a circular scratch could be made with a diamond 
point on the cover-glass. The disadvantage of this method is that the 
line is so fine that is difficult to find, and in the case of homogeneous- 
immersion objectives is obliterated by the liquid. The author has there- 
fore modified the apparatus by replacing the diamond point by a small 
brush with which a circular mark can be made on the cover-glass. Its 
mode of attachment to the Microscope must be given in the author’s 
own words : — “ This brush was attached to a piece that could be made 
eccentric, then this to another, rotating on a central axis, which was 
screwed into a piece with Society screw, which in turn could be attached 
to the nose-piece.” 
Sawing Bock-sections. J — For this purpose the Geological Survey in 
Washington uses a band-saw, which consists of an endless steel wire 
1/8 inch thick, running at a high rate of speed over two fly-wheels. 
* Central-Ztg. f. Optik u. Mechanik, xvi. (1895) pp. 25-6. 
t Amer. Micr. Jouru., xv. (1894) pp. 337-9. J Tom. cit., p. 350. 
