Additional designations are: Ropa, ropianka, (Galician Polish) pacura (Roumanian), Huile de naphte and pétrole brut (French); erdoel, rohoel, rohnaphtha (German); yenan (Burmese); sekinoyn (Japanese) shi-yu (Chinese); chapapote (Mexican). There are also a large number of names for such petroleum products as paraffine, or mineral wax, of which the Spanish brea is an example; and for asphalt, which is really petroleum in a dense form. Surface indications of petroleum and natural gas are frequent and diversified. The most common is in the nature of seepages, which are generally found in what are geologically highly disturbed areas, underlain with petroleum deposits. These seepages most frequently occur where the oil-containing formations have been folded and exposed on the surface, either when the folding took place or subsequently through the cutting of water courses. From these formations the oil seeps out and is shown as a coating on the streams or, in case the quantity is great or the oil very heavy, it is shown as asphalt deposits, of which there are many in Mexico, and of which the best known are the pitch lakes in Trinidad and Venezuela. It is a common occurrence in oil fields, more particularly those in the younger geological formations, to find mud volcanoes, probably caused by the escape of gas, bringing with it some water, which reaches the surface as mud. These mud volcanoes vary from a foot or two to several hundred feet in height in different localities and frequently cover an area of several acres. Another evidence of petroleum is found in Galicia in the form of ozocerite, which is in many ways similar to paraffin, but has some distinctive characteristics. This ozocerite is found on the surface or in mines. It exists in nature frequently in the form of lumps of several pounds of weight and more commonly impregnating the shale from which it is removed by boiling and removed as a scum on the boiling water. [Illustration: A temporary oil reservoir in Oklahoma. When petroleum is produced in advance of the erection of tanks it is held by earthen dams] Petroleum is found in different parts of the world and even in different formations in the same locality with widely different properties and composition. In some cases the oil is found almost white and varies through all the shades of amber and brown to black. It is found as highly liquid as gasoline and with a viscosity such that it will hardly run away from the hole--almost as viscous as the asphalt used for pavements.