1) utilizes the increased pressure in the open mouth of a straight tube facing the wind, and the decrease of pressure caused inside when the wind blows over a ring of small holes drilled through the metal of a vertical tube which is closed at the upper end.
On the whole, the best statistical source for this information is the annual computation published by the Archiv fiir Eisenbahnwesen, the official organ of the Prussian Ministry of Public Works; but the figure quoted above utilizes the Board of Trade returns for the United Kingdom and the report of the Interstate Commerce Commission for the United States.
The second process is one patented by Fritz Ullmann of Geneva, who utilizes chromic acid to oxidize the phosphuretted and sulphuretted hydrogen and absorb the ammonia, and this method of purification has proved the most successful in practice, the chromic acid being absorbed by kieselgiihr and the material sold under the name of "Heratol."
In his poems he mystically utilizes the connexion of the name with the same word meaning "wine-cup."
Nature not only distinguishes between active and passive surfaces in flying animals, but she strikes a just balance between them, and utilizes both.