Plate 17-20 of 1921 cloud chart. 17. Strato-cumulus or alto-cumulus from an
altitude of about 1,750 meters.... 18. Ragged strato-cumulus rolls below
fibrous alto-stratus.... 19. Strato-cumulus rolls, with strong east wind at
surface. 20. Ragged strato-cumulus rolls at 800 meters altitude in NW wind in
winter. Inset: same clouds viewed from height of 1,100 meters.