Duplicates atmospheric conditions in the upper air during cloud formation. Consists of a special flask with side opening fitted with rubber hose, pinch cock and large thick walled rubber bulb. When bulb, holding small amount of water, is compressed while side tube is open, air is forced from the flask. Fill flask with smoke by holding the inlet near a match and release bulb. Next close side opening. Then, by compressing and suddenly releasing bulb, dense cloud forms in flask. Instruction sheet is provided.