"The first documented telescopic rifle sight was invented between 1835 and 1840." - from Wikipedia. Their article states that scopes were produced with magnifications ranging from 3X to 20X. I recall seeing a picture of a DY with such a scope, with a startlingly long tube.

The Civil War foreshadowed modern warfare in many respects - trench warfare,machine guns (Gatling), repeating rifles, metallic cartridges, and the aerial dimension (hot air observation balloons), among others.
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Geezer in Chief