This lesson will describe the difference between transverse and longitudinal waves.

A graphic compares different types of dunes in terms of the presence of three parameters: wind, sand, and vegetation. Clicking an example reveals a photo and a sentence about the dune formation.

The technique of photographing objects observed under a microscope is discussed in this succinct site. Various pictures taken under a microscope are displayed on this site as well.

An advanced overview of map projections with illustrative graphics. Created by Peter H. Dana, Department of Geography, University of Texas at Austin in 1995.

With its clickable map, this site provides text and graphics on spreading boundary, converging boundary, subduction zone, transverse boundaries and faults.

The battering ram was a large beam, made of the trunk of a tree, and having a mass of bronze or iron fastened to one end, and resembling a ram's head. This shape, as well as its name, was given to the engine in question, on account of...