Distillation is the only process to obtain absolutely pure water. In the United States navy water aerated during distillation and run through a bone black filter for the purpose of improving its taste is exclusively used for drinking purposes.

Pewter has been used in most countries of the Old World for the last 2000 years. It was the substitute for silver and was to be found upon the tables of the well-to-do classes of the Middle Ages. Later it took the place of "treene"-wooden dishes, platters and bowls-in the homes of the peasantry and it was in general use until superseded through the adoption of cheaper materials, china, earthenware and Britannia metal. Like silver fine pewter oxidizes slowly, and unlike those of copper or brass, its oxides are harmless. Tim forms the greater part of pewter, the finest varieties, sometimes called "tin and temper," being simply hardened by a small portion of copper. Ordinary pewter is a mixture of tin and lead. The law of France restricts the content of the lead to 16.5 per cent.,this mixture being claimed as proof against sour wine and vinegar. Britannia metal is really a pewter of good quality, containing tin, antimony and copper.

While tungsten is considered one of the rare elements, tungsten compounds are of considerable use. Sodium tungstate is largely employed for impregnating fibers to make them fire-proof. It is also used as a mordant in dyeing. Tungsten bronzes are largely employed as bronze powders and pigments. The chief consumption of tungsten in recent years has been, however, for highspeed tool steels and for hardened steel for armor plates and large guns.

The blood rains of Central Asia and Mediterranean areas are showers of grayish and reddish dust mingled with rain. The dust is largely made up of microscopic organisms, especially she shells of diatoms, the red color being due to the presence of a red oxide of iron. These rains occur where violent huricanes, following periods of drought, carry the dust from dried lake bottoms and river beds into the upper regions of the atmosphere. At times the dust is transported hundreds of miles before it is precipitated, and it may even reach the high altitudes and be carried down by snow in which case the phenomenon is red snow.