NOTES ON AN EASY METHOD OF CAMERA LUCIDA DRAWING

Transcription

1 238 JAMES SMALL cellulas minutissimis triangularibus; lamella extema membranae saepe in forma mitrae circularis vel quadrangularis soluta est; chromatophora singula (?) in quaque ceuula cum pyrenoide; multiplicitis non satis cognita. Diam. coenob., ca. 35/i,; diam, cell., io-14/x. My thanks are due to Prof. F. E. Fritsch for the generous help he has given me in studying this little organism. GRANVILLE SCHOOL, LEICESTER. NOTES ON AN EASY METHOD OF CAMERA LUCIDA DRAWING BY JAMES SMALL (With 2 figures in the text) A COMBINATION of Baker's " Reflex Drawing Apparatus " with an J\ Ediswan "Pointolite Lamp" has proved so satisfactory in working that these notes have been written to make known the ease and speed with which a clear camera lucida drawing can be made by this method. The Reflex Drawing Apparatus^ is a small right-angled prism with the 45 side silvered (the whole protected by metal fittings), which is affixed by means of a small screw upon the top of any ordinary eyepiece. It possesses several advantages over the larger mirrors in common use. Firstly, it is small, convenient to handle, easily adjusted, and when affixed to the eyepiece it can be readily turned up so that the field may be viewed through the mirror from above. Secondly, the mirror surface is protected by glass which is exposed only to a small extent; this largely obviates the numerous cleanings necessary with the larger mirrors, and the deterioration of the surface which is a consequence. Thirdly, since the rays pass into ' Sold by C, Baker, 244, High Holborn, London, Price, 17s, 6d.

2 Notes on an Easy Method of Camera Ludda Drawing 239 and out of the glass at right angles to the surface, double reflections are avoided and the reflecting apparatus becomes as efficient as a simple metallic mirror. The " Pointolite " outflt^ is becoming so well known, and is, indeed, so rapidly becoming one of the recognised pieces of equipment for microscopic work, that description is unnecessary. Special stands and holders for the lamp are supplied, but in the present case the lampholder was attached to a heavy base with a universal ball and socket joint which happened to be available. For drawing purposes the lamp is arranged in the vertical position and covered with an oblong pmhead LAMP Fig. I Fig. 2 case of cardboard. This case (Fig. i) has a small notch in the base, through which the flexible wire is passed, allowing the base of the case to rest flat upon the bench. In one side of this cardboard cover and exactly on a level with the small "pinhead," which forms the source of light, a round hole not more than three-eighths of an inch in diameter is cut. The substage mirror is removed from the microscope, or swung to one side, and the microscope is tilted into the horizontal position. The height of the tube in this particular case is slightly less than that 1 The Standard ioo candle power lamp has been used (cost 24s.) with the Standard Universal Resistance Box and fittings (cost ^5, less 33^ %), as supplied by the Edison Swan Electric Co., Ponders End, Middlesex.

3 240 JAMES SMALL of the hole, and the instrument is raised by flat wooden blocks until the optical axis is on a level with the centre of the hole and with the glowing pinhead of the lamp. It is pushed as close up to the hole in the cardboard casing as the stand will allow. The section to be drawn is then inserted, and the chosen field illujninated as evenly as possible and as brightly as is compatible with clear definition of details. The Reflex Drawing Apparatus is now screwed on (the appearance of the field can be checked by turning the mirror upwards) and then the mirror is turned so that a bright, clear picture showing details and colouring as in the direct view is thrown upon paper placed flat upon the bench. The brightness of the image upon the paper varies, of course, with the amount of light from other sources. The stray beams from the hole in the cardboard casing have little effect, if the apparatus is properly fixed up. The image is faint in full daylight, but in twilight or when dark blinds of the now usual type are pulled over the windows the image is quite bright. Final adjustments of brightness can be made easily by using (i) a half cover of cardboard (Fig. 2) which shades the image from all extraneous light^ except from the observer's direction and his shadow acts very efficiently from that side; (2) an ordinary night-light which can be moved about until lines drawn upon the paper are visible while the image still remains clear. Nothing more remains to be done now, except to draw lines in pencil or in ink around the outlines of cells and to fill in as many other details as are required in the same way; the actual process of drawing becomes easier and more rapid than tracing with transparent paper. The advantages of this method are firstly, the ease with which the adjustments can be made when the apparatus has been in working order; secondly, the brightness and clearness and flatness of the image which make it possible to work in daytime without a darkroom; thirdly, the ease and comfort with which a camera lucida drawing can be made when one has the paper fiat upon the bench and when both image and paper are viewed directly, and not one or other as a reflection; fourthly, the comparatively low price of the apparatus, especially when it is considered that apart from the refiex mirror the rest of the apparatus is useful for so many other illuminating purposes. The total cost is, in fact, less than that of many of the usual camerce lucida. ' These cardboard cases can be made easily by ruling heavily with a blunt point the lines for folding, and then fixing the edges which overlap with splitpin paper fasteners or drawing pins.

4 Notes on an Easy Method of Camera Ludda Drawing 241 One of the great difficulties in making drawings of consecutive portions of a large section is that the end of one portion only fits exactly to the beginning of the next portion when the plane of the drawing paper has been very accurately adjusted in the same plane as the object or the image. Using this method, one can move the section by hand or on the mechanical stage and leave a part of the section already drawn still in the field. This part can be fitted easily on to the drawing by moving the latter in the direction followed by the moved image. The outlines of both are clear and can be superimposed quite accurately and easily, and then the drawing of the new portion can proceed! These adjustments only involve the turning of the mirr&r into the correct plane and this can be done rapidly, because it is only necessary to get a circle of light and not an ellipse. If two diameters of the illuminated zone at right angles to each other are equal the adjustment of the mirror is accurate. As examples of diagrams drawn in pencil or directly in ink by this method in from two to ten minutes readers are referred to my Textbook of Botany (Figs. 148, 150, 270 a, 395, 399, 400), while for detailed drawings occupying never more than one hour, and sometimes only fifteen minutes for the pencilling, they may note the Figures 149, 151, 153, 154, 157, 268, 270 b, Tj/\, 308 and 396 in the same volume. BOTANICAL DEPARTMENT, QUEEN'S UNIVERSITY OF BELFAST.

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