a cromlech is a form of:

Self-acting



noun
1.
(automatic. Able to act or work automatically) ស្វ័យចិត្ដ
ENGLISH MEANING
adjective
1.
Acting of or by one's self or by itself; -- said especially of a machine or mechanism which is made to perform of or for itself what is usually done by human agency; automatic; as, a self-acting feed apparatus; a self-acting mule; a self-acting press.