THEY LOOK AS COMPLEX and involuted as machines themselves. But if the ensemble is hard to remember, the large masses of these paintings are immediately felt. The eye notes a thousand independent shapes entered into a pattern that has yielded to them without interrupting its flow. The more simplified “technological” styles of Western Europe—in Holland, France, Germany, and Russia—are not more monumental. Rivera’s pictorial economy takes into itself the insatiable need to show how things work and his frescoes, loaded with an almost bewildering amount of information, are more descriptive than any