Currents may also be generated by density differences in water masses caused by temperature and salinity variations. These currents move water masses through the deep oceanâtaking nutrients, oxygen, and heat with them. Occasional events also trigger serious currents. Huge storms move water masses.
Ray-ban and most other manufacturers frames are made from Plastic compounds. Ray-ban used to make all its glasses out of 'glass'. Now it makes its sunglass products out of scratch resistent plastics. Often they will 'feel' like glass but are in fact most usually plastic production.
electric lenses. Further developments by Pentacon were the outer appeareance of the lenses which was changed to more modern black lens barrels with white, green and red inscriptions, and the electric lens series which was made for the Praktica electric SLR body series.