ON MICROSCOPICAL DEAWING AND PAINTING. 169 



lines are fixed ; the eye (unsteady at the best) and 

 the pencil point must be in unison. Keeping the 

 pencil on the paper preserves " the place." 



In arranging any object for drawing, it should be 

 sufficiently magnified to show everything bearing 

 upon its elucidation, and, as a rule, an isolated 

 subject, a complete form, ought to occupy, as 

 nearly as possible, the entire field. Some specimens 

 necessarily overflow the circle surfaces of injected 

 preparations, botanical sections exhibiting features 

 requiring the highest magnification consistent with 

 the preservation of a focal plane which, obviously, 

 cannot be fairly disclosed (except at a loss of im- 

 portant detail), are beyond the scope of the circle 

 of popular survey. It must then be abandoned, 

 the drawing spread out, and made in sections by 

 shifting and combining visions. Using the camera- 

 lucida any part may be carefully drawn, making 

 two or three (if angular, the better) prominent 

 points, corresponding with similar appearances in 

 the subject. These marks or tri-angulations (as 

 near the margin of the field as possible), must be 

 remembered, the position of the object is then 

 moved by stage adjustments, and another part of 

 the field arranged, the included marked points are 

 coincided, by shifting the block of paper, and further 

 outlines expanded ; in this way the camera-lucida 

 may be used under high powers with four or even 

 six combinations of vision and the parts, with 

 care, will " read into " each other, and result in 

 a drawing of considerable dimensions, perfectly 

 mapped, and true in contour ; it may then be con- 

 tinued part by part. 



After faint outlines and points of certainty are 



