178 METHODS OP MICROSCOPICAL EESEAECH. 



brushes of sable are required, the hairs short and 

 coming to a fine point, they should be of the best 

 make, no brush that has touched Indian ink can be 

 used for delicate colour, and those employed for 

 carmine, yellow, and blue, should be marked and 

 kept distinct ; the same applies to pens, often re- 

 quired, but the pen carrying colours must be used 

 with extreme discretion. If a fine line can be 

 obtained with the sable, it is of higher quality, 

 moreover with the handy pen the temptation is 

 great to obtain hurried results by strokes and dots, 

 but for pure black and white memoranda, or repre- 

 sentations requiring speed, nothing can equal a fine 

 pen charged with indian ink or neutral tint, re- 

 membering never to approximate or cross a line 

 until it be properly dry ; with this precaution a pen 

 drawing may approach the semblance of an etching. 

 The colours should be dry cakes, the palette pre- 

 served as pure as possible ; moist pigments rubbed 

 from pans become contaminated, and even dry 

 cakes should be kept separated ; loose and in con- 

 tact they chip and soil each other. Quality is all 

 important, use only those which are " transparent." 

 Manuals on painting contain lists of recommended 

 pigments and their qualities, and generally receive 

 no attention ; for the work in question it may 

 remove difficulties to remember that important 

 colours are neutral tint, Payne's grey, Antwerp 

 blue, carmine, scarlet lake, yellow ochre, Hooker's 

 greens, Nos. 1 and 2, and raw Sienna colours to 

 avoid, vermillion, cadmium, the umbers, emerald 

 green, and Vandyke brown. These are densely 

 opaque, and " load " too heavily for delicate work ; 

 a good test is to rub a portion of each cake of a 



