In 1693, the postage rate of a letter was determined by how much light went through the letter. The less the light went through the letter the more expensive the rate would be. This technique was referred to as candling.

The postage rate for a letter in 1693 was determined through how much light could pass through the letter. The postage rate would be more expensive if less light went through, and this process was called candling.

The Earth experiences 50,000 Earth quakes per year and is hit by Lightning 100 times a second.

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