TOOLS AND EQUIPMENT

these was the cauterium^ a kind of spatula of metal, with a rounded end. It may
have resembled those in figure 23, c and d* Many of the Fayum portraits show in
their conformation the marks of a blade of this sort and have somewhat the look
of modern oil paint that is spread with a palette knife.

Cestrum. Like the cauterium, this was a metal spatula used for painting in
ancient times. It was, however, different in shape, being pointed and more like
a stylus. Eastlake (I, 154) gives as synonyms for it, mriculum and rhabdlon.
Pliny (XXXV, 149) mentions the oestrum and, from the context, it appears that
this must have been an instrument that was usually heated.

FIGURE 5. Two types of camera obscur a—drawings adapted from illustrations in Meder.
At the left (p. 550, fig. 256) is a cross section of an early construction in which the image
falling through the lens is reflected by the mirror (a) onto a drawing glass or tracing
surface (£). At the right is a French camera obscura of the second half of the XVIII
century (p. 551, fig. 257). This is a large box in which the draughtsman sits, closing the
door behind him. The image enters at the side opposite that shown here, through a lens
in the small box at the top. From there it is deflected by the glass (a) onto the drawing
surface (£). At c is the seat for the draughtsman. Heavy metal straps at the side of the
box are to hold poles by which it is carried.

Chalk* The regular black chalk used for drawing is a natural deposit, a slaty,
soft, earthy material, very rich in carbon. In Europe it is found mainly in Thurin-
gia, parts of France, and Andalusia (Meder, p. 109). Other colors, chiefly a range
of earth reds, are common in practice and are available in the stocks of artists'
colormen. The white chalk used for drawing—to be distinguished from the white
chalk that is an inert used for grounds—probably has included a number of dif-
ferent materials such as sticks of gypsum or steatite (soapstone). As now prepared
for the market, the various colors of drawing chalk are put up in small sticks or as