Spirit might SO overwhelm the novice that the excess of power had
to be forcibly expelled and the individual controlled by members
of the ceremonial appointed for the purpose.

Tribal masks display immense variety in form, size and detail.
Many hundred examples have been lost, ignorantly defaced, destroyed,
or suffered to decay by neglect; yet the finest surviving speci-
mens show high standards in fertility of imagination and of execu-
tive and mechanical skill, especially when the fact is realized
that the only tools available were stone or jade chisels and
knives with the incisor teeth of beaver for the finest details.
They include not only realistic and traditional representations
of the animal world but of human faces also, expressing pain,
disease or death. Portrait masks particularly show exquisitely
modelled contours full of skill and subtlety. By the use of
strings only, assisted by ventriloquism and the conjuror's art,
uncanny realism was imparted to special masks. Tongues protruded
and were withdrawn; telescopic noses lengthened, eyes glared or
rolled weirdly; movable heads and limbs shook and shivered; vivid
illusions being assisted by the flickering flames of a great cen-
tral fire, the sole form of light. Some masks show double faces,
back and front; others split open and reveal a human face within
a huge bird's beak or a representation of the sun. Others were
so small and shallow they might cover only the forehead.

Two classes of masks are to be distinguished among the tribes
of British Columbia:

(1) Those attached to house-front and heraldic poles. Many of
these were very large and some of them were compound, the
outer sides opening to show a human face within; others,
such as that depicting Sis-i-utl (the Double-Headed Snake)
had moveable parts, (see Plate 9, Figure 1) while others
were more akin to house-front paintings. To understand
their full significance calls for considerable insight into
the social organization of each tribe.

(2) Dance Masks. These were again subdivided into

(a) Potlatch masks, often representing the principal crests
of the owners, which were allowed to be used in summer
and by daylight.

(b) Secret Society masks, representing mythical spirits and
traditional ancestors, of which the use was strictly
confined to the winter months. The wearers took part
in the dranatic dances associated with music and song
performed at night in the great communal houses, when
semi-darkness enhanced their weird effects; for it was

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