Atomic structure for educational use of carbonic acid Czechoslovakia 1950s.

Educational botanical model in section of the sunflower flower showing its inner part, this is an enlarged and decomposable inner tubular corolla of a concrescent petal section in th...

Didactic anatomical model of an enlarged jaw, mounted on a wooden board with hooks for hanging. In evidence the circulatory system, the roots of the teeth, and two caries. Made in ha...

Pair of molecular atomic structure models for chemical didactic use. The spheres are made of painted wood and represent atoms and a molecule. The base...

How high is the water, mama? Johny Cash was asking his mother, when it is was '6 feet high and rising'. In Egypt it would probably mean that taxes that year would be low. In Egypt it all depended on the behavior of the Nile and a Priest, who would monitor the so-called Nilometer. A nilometer was a structure for measuring the Nile River's clarity and water level during the annual flood season. If the water level was low, there would be less food. If it was too high, it would be destructive. There was a specific mark that indicated how high the flood should be if the fields were to get good soil. Their predictions would determine how much money...