ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 527 



cardboard iu the usual way. Auy loss from the chamber by evapo- 

 ration is prevented by occasionally wetting the cardboard on the slide.* 



Arrangement of the Miero-speetroscope.f — Dr. C. A. MacMunn 

 uses for the researches recorded siqva p. 429 a binocular Microscope 

 provided with a substage achromatic condenser, to which are fitted 

 two diaphragms. The objectives are so adapted as to enable both 

 fields to be fully illuminated when any power up to 1/8 in. is used. 

 The left-hand tube is used as a " finder," and as a means of getting 

 any required portion of the object into the centre of the field so that 

 its spectrum may be obtained in the spectrum eye-piece of the 

 right-hand ttibo. In this way the various portions of a very small 

 piece of tissue or organ may be readily differentiated from each 

 other, and their spectra observed. By the use of the iris diaphragm, 

 which is placed below the substage condenser, the marginal j)art of 

 the field can be readily cut off. A compressorium is indispensable to 

 squeeze out the sections thin enough to allow the spectrum to be 

 observed. 



Examining the Spectrum of ChlorophylLi — Mr. F. 0. Bower 

 and Dr. S. H. Vines recommend the following as a convenient method 

 of examining a solution of chlorophyll spectroscopically. 



The tube of the Microscope is withdrawn and replaced by a glass 

 tube, the bottom of which covers the opening of the stage ; the sides 

 of the tube being rendered oj)aque by wrapping round them a sheet 

 of black paper. The solution is then poured into the tube and into 

 the opening of the latter a microspectroscope is introduced. Light 

 is then reflected on to the bottom of the tube by the mirror. The 

 advantage of this method is, it is said, that it enables the observer 

 to vary the thickness of the layer of the solution to be examined. 



Multiplying Drawings.§— Mr. C. M. Vorce calls attention to the 

 ferro-prussiate process for this purpose. Let the camera- lucida 

 drawing be made with good black ink directly upon tracing-paper 

 placed over white paper, or it may be di-awn on white paper and care- 

 fully traced on tracing paper. In either case, when dry, gum the 

 tracing paper on a sheet of clear glass, with the drawing next the 

 glass ; it may then be printed from as an ordinary negative, and any 

 lettering will be produced in its proper position. With suitably 

 prepared ferro-prussiate paper in clear sunlight it prints quicker 

 than an ordinary gelatine negative ; from 10 to 15 seconds will suffice 

 for well-made drawings on clear paper. The copies are thus made 

 very quickly in any number, and are rinsed in water, and dried much 

 more quickly than an equal number of silver prints could be toned 

 and fixed. Fine details are well reproduced. 



As the plan proposed by Mr. Vorce does not dispense with the 

 necessity of camera-lucida drawings, which seems to be a desideratum, 



* Bower and Vines's 'Course of Piactical Instruction in Botany,' 1885, p. 16. 

 t Proc. Physiol. Soc, 1884, No. 4. See Nature, xxxi. (1885) pp. 326-7 

 (1 fig-). 



% Bower and Vines's ' Course of Practical Instruction in Botany,' 1885, p. 42. 

 § Amer. Mon. Micr. Journ., v. (1884) pp. 207-S. 



