This wall map of Iran from the Perry-Castaneda Collection is comprised of seven individual maps showing many aspects of Iran. Clicking on the individual map will enlarge it for your perusal. You can also click on the text to see a brief...

Benjamin Franklin (January 17, 1706 - April 17, 1790) was one of the Founding Fathers of the United States of America. A noted polymath, Franklin was a leading author and printer, satirist, political theorist, politician, scientist,...

Lengthy biography of Euler that sets him in relationship with his contemporaries in mathematics and physics. Several quotes and pictures available, as well as links to relevant mathematical topics. A terrific site.

A very lengthy page from friesian.com discussing Bohr's theory of electronic energy levels and the explanation of commonly observed atomic emission line spectra. The concept of a photon and Einstein's observation of the photoelectric...

A very lengthy page from friesian.com discussing Bohr's theory of electronic energy levels and the explanation of commonly observed atomic emission line spectra. The concept of a photon and Einstein's observation of the photoelectric...

A very lengthy page from friesian.com discussing Bohr's theory of electronic energy levels and the explanation of commonly observed atomic emission line spectra. The concept of a photon and Einstein's observation of the photoelectric...

A very lengthy page from friesian.com discussing Bohr's theory of electronic energy levels and the explanation of commonly observed atomic emission line spectra. The concept of a photon and Einstein's observation of the photoelectric...

A very lengthy page from friesian.com discussing Bohr's theory of electronic energy levels and the explanation of commonly observed atomic emission line spectra. The concept of a photon and Einstein's observation of the photoelectric...

A very lengthy page from friesian.com discussing Bohr's theory of electronic energy levels and the explanation of commonly observed atomic emission line spectra. The concept of a photon and Einstein's observation of the photoelectric...

A very lengthy page from friesian.com discussing Bohr's theory of electronic energy levels and the explanation of commonly observed atomic emission line spectra. The concept of a photon and Einstein's observation of the photoelectric...

A very lengthy page from friesian.com discussing Bohr's theory of electronic energy levels and the explanation of commonly observed atomic emission line spectra. The concept of a photon and Einstein's observation of the photoelectric...

A commercial site giving information on the physical properties and history of emeralds. Includes details on the cuts and valuation of these gems.

A commercial site giving information on the physical properties and history of emeralds. Includes details on the cuts and valuation of these gems.

A commercial site giving information on the physical properties and history of emeralds. Includes details on the cuts and valuation of these gems.

" North China includes the densely populated and intensively cultivated North China Plain, the loess-covered uplands of Shansi, northern Shensi, and eastern Kansu, and the sparsely populated, semiarid steppes of Inner Mongolia....

A brief physical description of emeralds from an online database about minerals. Provides information about history, characteristics, color, and use.

This commercial site contains information about the sapphire's physical properties and where it can be found. Also discusses the history and romance related to the stone and includes a description of its quality.

This commercial site contains information about the sapphire's physical properties and where it can be found. Also discusses the history and romance related to the stone and includes a description of its quality.

Illustrated dictionary entry for Centaurs. Describes the physical attributes of Centaurs, famous Greeks they are tied to in history, and their function outside of mythical context.

Illustrated dictionary entry for Centaurs. Describes the physical attributes of Centaurs, famous Greeks they are tied to in history, and their function outside of mythical context.