HARDWICKE'S SCIENCE-GOSSIP. 



view well defined with a Ross No. l stand. The dis- 

 tance from the front of the objective to the edge of 

 the camera prism is about twelve inches, and from 

 the camera to the table surface (at right angles) 

 eleven inches ; the view projected on the circle of 

 jiaper placed on the table would consequently over- 

 lap : Ijlock should therefore be raised in any con- 

 venient way, until the field of the microscope and the 

 white circular space exactly coincide, the subject will 

 then be in fair proportion. Another advantage of 

 the black margin is, that if, when using the camera, 

 tlie drawing should slip, as it is very apt to do, the 

 dark circle will assist in replacing it. 



The light on the paper should be in excess of 

 the light from the object. In the employment of the 

 camera lucida, speed and precision are essential. 

 Quickly make easily recognised points and lines ; do 

 not linger over small matters ; nothing fatigues the 

 eye sooner than the use of this instrument. Indeed, 

 to manipulate it with advantage requires considerable 

 practice. No drawing can be greatly advanced by it. 

 Contours, salient points, and especially measurements 

 may be quickly and accurately fixed and drawn, but 

 any attempt at elaborate detail will end in confusion. 

 Useful as the camera is in the earliest stages, it 

 should be discarded as soon as possible. The 

 microscope is then placed in position, the lights 

 adjusted, and the drawing continued by actual 

 observation through the instrument. The blocks 

 should be made of carefully selected paper, thin, hard, 

 smooth. The drawing in its general details should be 

 made with a pencil of the best quality, extremely hard 

 and capable of taking a fine point, and yet not 

 tearing the surface of the paper. Tlie work may then 

 be corrected and improved with a fine pen charged 

 with Indian ink or Payne's grey, somewhat diluted. 

 If intended for painting, the drawing should never 

 be touched with rubber of any description, and no 

 attempt at shading should be made either by pencil 

 or pen. At this point the ability of the artist 

 begins to tell, and no written guidance can be offered 

 beyond some general hints, derived by experience, of 

 the character of objects best adapted for copying and 

 the method of exhibiting and illuminating them. 

 The light is of paramount importance : it should 

 be a movable argand gas burner, fed through a 

 flexible tube, capable of being raised or depressed, 

 with a green cardboard shade. The edge jujt 

 below the level of the flame in the shade ; circular 

 holes and slits may be cut for special purposes. 

 Of illuminating transparent objects little need be 

 said. Transmitted light from the simple mirror means 

 a good effect : it is obtained by allowing the rays of 

 light to pass through a piece of thin tissue paper 

 placed over the opening of the substage. Such 

 objects as the proboscis of blow-fly, tongue of 

 cricket, spiracles and other parts of insects cannot be 

 displayed to greater advantage. It may be mentioned 

 here that to have an effective drawing, the object or 



the part selected should be magnified to nearly 

 occupy the field of view. With sections of injections- 

 (opaque) such as tubercular lung, the whole field 

 would necessarily be filled. As high a power as is- 

 consistent with the preservation of a fairly plane 

 surface should be employed. The instruments for 

 light are the parabolic illuminator (see Carpenter, 

 5th ed. p. 141), a small plane convex condenser, on 

 separate stand, and, the most important of all, the 

 side reflector or silvered speculum (see Carpenter, 

 5th ed. p. 150) : the most useful form of speculum, 

 for drawing purposes, is that which has a separate 

 fitting to the stand of the microscope. That which 

 is attached by a spring clip to the objective is not so 

 efficacious in producing oblique rays, nor so com- 

 pletely under control in producing artistic contrasts 

 of light and shade by the primary object to be 

 attained. The lieberkiihn has a positive defect in 

 artistic illumination, it sends the light perpendicularly 

 all round the object, giving little or no diversity of 

 shadow, and cannot be- used with effect. 



In painting objects under the parabolic illumina- 

 tion, or with the side speculum, the painting of the 

 background should be treated with especial care, and 

 stippled up to the tone. Actually seen under the 

 instrument, the iridescent eggs of insects are gene- 

 rally attached to fragments of vv^ood or leaves, 

 parasitic eggs to feathers. These should be carefully 

 painted, and the background beyond stippled up to 

 the edge of the circle. Such objects make lovely 

 drawings. It would be difficult to particularise 

 subjects, suitable for drawings — so immense are the 

 resources. Many are so exquisitely beautiful, that 

 even with good management, cultivated taste, and 

 fair skill, the best representations fall far short of 

 the actual object ; but let not the student be dis- 

 heartened, for to render these things on paper in 

 their perfect integrity, it would be necessary, if sucli 

 a process could be conceived, to dip your brush in 

 light. All that can be hoped for, is a semblance. The 

 young artist may here be reminded that in his paint- 

 ing the most exalted light at his command is the 

 pure white of his paper, which should be always 

 jealously preserved. A prepared specimen, or slide, 

 should be perfect, but many most common objects 

 of easy access hastily arranged, form admirable sub- 

 jects for the purposes of drawings. 



Some years ago a work on the microscope was 

 published by the late Richard Beck. It contained a 

 plate representing a mere splinter of lucifer match 

 under reflected light. Nothing is more suggestive 

 than such a drawing as showing the accessibility of 

 subjects. Of preparations there is a wide field. A few 

 may be mentioned. Sections of shell with a dark 

 ground or parabolic illuminations. A portion of the 

 field should be disclosed to be carefully stippled up 

 to an even tone, some degrees lower than the black 

 margin ; polycistina and foraminifera, under parabolic 

 illumination. Power to be used two-thirds. The shells- 



