ON MICEOSCOPICAL DRAWING AND PAINTING. 171 



over another until the first be perfectly dry ; stip- 

 pling should show a granulated appearance, lost 

 when touches are allowed to run into and become 

 absorbed by each other. 



Illumination, and its diversities for art work, are 

 of as much importance as the amplification. Power 

 and light should be adapted to each other, and 

 to the character of the subject, its mode of prepara- 

 tion, and what it is expected to reveal. The light, 

 whether from gas (argand burner), or oil, should be 

 capable (in the case of gas, by means of flexible 

 tubing,) of being placed in every possible position, 

 from the surface of the table to, or even above, the 

 level of the stage. Ordinary transparent objects, 

 under low powers, are sufficiently shown with 

 transmitted light from the mirror, modified through 

 a diaphragm of waxed tissue paper ; ordinary pre- 

 parations of insects cannot be better displayed ; the 

 best reflected light is from the side speculum, col- 

 lected from a flame through an intervening plano- 

 convex lens, on a separate stand. In all observations, 

 even the simplest, accuracy of liglit-focus (often 

 neglected) is important. For powers beyond the 

 half -inch, transmitted light is aided and improved 

 by the purity and control afforded by the achromatic 

 condenser, an instrument in the hands of novices, 

 not always well managed, or sufficiently appre- 

 ciated ; focussing on the same plane as the object, 

 the source of light, it is capable of regulating 

 intensity, purity, and deviation of rays by aper- 

 tures and stops, with which it is supplied and thus 

 the most varied combinations may be secured. Its 

 use should be thoroughly mastered, as it produces 

 the most beautiful, instructive and even amusing 



