When were window envelopes first used?

Answer Window envelopes were patented in 1902 by Americus F. Callahan. His patent stated that the holes in the envelope would be covered by transparent paper. That original design is very much like the wi... Read More »

Top Q&A For: When were window envelopes first used

How old were you when you first used a tampon?

I was 12 when I got my period, and I'm 14 and don't wear tampons. I've tried twice, but they just don't feel right, so I take them out. I perfer pads,soo...

When were bar codes first used?

In 1948, Bernard Silver, a graduate student at Drexel Institute of Technology in Philadelphia made the first step in the use of bar codes. Silver and Norman Joseph Woodland, a twenty-seven-year-old... Read More »

When were airbags first used?

Airbags were first conceived as an automotive safety device in the early 1950s, with the first patent granted to John Hetrick in 1953 for a "safety cushion." However, airbags did not become a real... Read More »

When were exponents first used?

While the Egyptian Ahmes Papyrus (2000-1800 B.C.) is the oldest known mathematical computation document that uses a type of math that could be translated into exponents; two Indian Beez Ganit vedas... Read More »