A process in nature in which organisms possessing certain genotypic characteristics that make them better adjusted to an environment tend to survive, reproduce, increase in number or frequency, and therefore, are able to transmit and perpetuate their essential genotypic qualities to succeeding generations.
A watchglass can be used as a beaker cover, but you can also place small amounts of chemicals on it and then heat it (for example, to evaporate some water from a wet chemical). From Wikipedia: A watch glass is a circular, slightly concave piece of glass used in chemistry as a surface to evaporate a liquid, or as a cover for a beaker. The latter use is generally applied to prevent dust or other particles entering the beaker; the watch glass does not completely seal the beaker, and so gas exchanges still occur.
The Purpose of Jewels in Watches. When a watchmaker speaks of the jewels in a watch, he or she is not talking about the decorative jewels that may adorn the exterior of the watch case; the watchmaker is referring to jewels which are used within the mechanism of the watch itself. The purpose of the jewels in the watch is to reduce friction. Jewels provide a very smooth, very hard, long-lasting bearing surface at various points within the watch in order to reduce friction and increase running efficiency.