In order to make it easier to describe elements and molecules, chemical formulas are used. For example, H represents one atom of hydrogen and O represents one atom of oxygen. If we want to represent two atoms of hydrogen, instead of writing H H, we write H2.
This car is named for Promontory Summit, Utah, just north of Great Salt Lake and the site selected for the joining of the Union Pacific and Central Pacific Railroads. Completion of the railroadâthe greatest engineering feat of the 19th centuryâculminated in a celebration there on May 10, 1869. Promontory Point, often erroneously referred to as the location for the ceremony, juts out into the lake itself. It was the location of a saltworks for many years.
This 12-story lighthouse off the California coast was expensive to build, and even drove some workers mad, but it has saved countless lives by warning ships off from a treacherous patch of rocks. Finished in 1891, the lighthouse was built right into one the reef rocks. A number of workers lost their lives constructing it and life as a keeper of the property wasn't much saferâat least five keepers died on the job.