ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



807 



after the object has been arranged on the central square, cover the whole 

 with a thin circle and cement it fast by running a warm wire around the 

 edge to melt the wax. A small drop of water may be placed in the 

 annular space if desired. The thickness of the slip and square, and the 

 depth of the cell must of course be determined by each worker according 

 to his needs. The secret of success here is, to be sure that the joint 

 between the ring and the slip is air-tight, and to firmly secure the cover, 

 using an abundance of wax. 



Lamps for Microscopical Work.* — The Editors of 'The Micro- 

 scope ' consider that in the efforts to put before the microscopical public 

 attractive illuminating apparatus, writers seem to have lost sight of the 

 excellencies of the humble hand-lamp. Beginners are thus led to pur- 

 chase the expensive German student's lamp or some still more costly 

 microscopical lamj). It can safely be asserted that for the general pur- 

 poses of the working microscopist, a small hand-lamp giving a broad, 

 flat flame (such a lamp as can be bought anywhere for 25 or 30 cents) is 

 superior to any of the expensive lamps made especially for the pur- 

 pose, and we are convinced from our observation of the methods 

 of many microscopists that this is not realised by many except the 

 experts. 



By the size of the flame and the distance of the lamp from the Micro- 

 scope, the intensity of the light can be readily adapted for any work, 

 from the use of the lowest powers to the examination of histological and 

 biological specimens with the highest immersion lenses. For bacterio- 

 logical work with the 1/12 in. or 1/18 in. immersion lenses this 

 light is unsurpassed. In the examination of opaque objects this lamp 

 is not so convenient, as it is necessary then to have the source of 

 light at quite an elevation. It is very easy, however, to improvise a 

 stand. 



Tubes for Microspectroscopic Analysis.! — ^oi* microspectroscopic 

 analysis it is necessary to be able to alter the depth of the liquids ex- 

 amined and to know exactly what these depths are. Three forms of 

 tubes answer these requirements. The first is a prisniatic tube with 

 the same proportions as that of the author's (M. L. Malassez) first 

 hgemochromometer, so that the glass plates at the end of a length of 

 10 cm. are 10 mm. apart ; consequently at distances, say, of 1, 2, or 

 3 cm, from the top the thickness of the liquid layer is 1, 2, or 3 mm. 

 A millimetre scale placed along the side of the tube indicates the depths 

 corresponding to different points in the length. 



In the two other tubes there is an internal sliding tube (" tube 

 plongeant "). The simpler form consists of a metal tube, 2 to 3 cm. 

 long and 5 mm. in diameter ; the lower extremity is closed by a piece of 

 glass, and the upper expands like a basin. This is the tube into which 

 the liquid to be examined is poured and it is placed in the aperture of 

 the Microscope stage where it is held by the expansion at the upper end. 

 The tube which slips into this is made of metal, and is a little longer 

 and narrower than the outer one. Its lower end is closed by a glass, 

 and its upper screws into the Microscope tube in place of the objective. 

 By screwing down the Microscope tube the layer of liquid is thereby 

 diminished. If on the Microscope tube there is a millimetre scale, and 



* The Microscope, viii. (1888) p. 206-7. 



t Arch, de Physiol., viii. (1886) pp. 268-71 (1 fig.). 



3 I 2 



