Final answer:
The chemist who observed his younger sister mixing petroleum jelly and cold dust to apply eyelashes for a darker fuller look is not specified. However, the use of cosmetics dates back to ancient times, with the Egyptians using makeup to enhance their appearance.
Step-by-step explanation:
The chemist who observed his younger sister mix petroleum jelly and cold dust and apply eyelashes to the eye for a darker fuller look is not specified in the provided information. However, the use of cosmetics and the development of different cosmetic products have a long history.
In ancient times, Egyptians used makeup to enhance their appearance, including eyeliner and eye-shadows in dark colors. They also used kohl and castor oil as protective balms.
It is important to note that the use of cosmetics has been supported and criticized throughout history, and different cultures have varying perspectives on their usage.