The Arts and Crafts School of Paris was in need of an auditorium, with accommodation for one thousand persons, suitable for lessons and lectures. Owing to lack of space, it was decided to build it underground, below one of the courtyards. The choice of roof shape was an ellipsoid of revolution, whose major axis is inclined to the horizontal. The maximum diameter is 32 ms and maximum height is 10 ms. The thickness of the roof structure is 50 cms along the lower part, and 20 cms near the crown. This solution was of special interest as it overcame simultaneously two difficulties; namely, the foundation, when this has to be based on fill soil, and the non-interference with the illumination of nearby buildings. In this case the loading on th...