] 24 Proceedings of the British Association. 



amount gradually increases, till wheat weighing 581b. per bushel 

 gives 1 .75 per cent. — 6th. The practical question then follows : — How 

 much inorganic matter is removed from the soil of an acre of land 

 by the grain of a crop of wheat ? The answer is, one pound per 

 bushel. 



* Analyses of Three Species of Fucus,' by E. G. Schweitzer. — 

 These analyses were undertaken with a view to ascertain the causes 

 which render one kind of fuci beneficial as a manure, whilst other 

 kinds do not succeed. It was found that in the Laminaria saccharina 

 the alkaline carbonates predominated, whilst in the Fucus vesiculosus 

 and Fucus serratus there was an excess of the sulphates ; and in the 

 Laminaria, potash is found in larger quantities than soda, whilst the 

 contrary is the case with the Fuci. The quantity of iodine in Laminaria 

 was also greater than in the other two. Some experiments were tried 

 to ascertain if the Laminaria exhaled iodine under the influence of 

 sunshine, but no such exhalation could be detected. The analyses 

 were exceedingly minute, giving twelve and thirteen constituents de- 

 termined. 



Prof. Johnston made some remarks on the imperfections of our 

 knowledge of the chemical principles of Rotation, the difficulty having 

 been the length of time required for a full investigation of the 

 subject. He objected to the opinion expressed by some chemists, 

 that any crop may be grown on the same soil for any length of time, 

 by the application of manures, the quality of which were to be decided 

 by analysis. In addition to chemical considerations, the physical 

 conditions of the soil are to be taken into account. Several points 

 were shown to require strict attention, particularly the structure of 

 the plant itself, and the character of its root, which he had observed 

 to vary with the conditions of the soil. 



< On the Voltaic Reduction of Alloys/ by C. V. Walker.— This 

 communication was intended to explain the methods by which the 

 author has succeeded in throwing down metallic alloys from compound 

 solutions by the action of galvanic electricity. The process adopted, 

 is to prepare a strong solution of cyanide of potassium, and com- 

 mence electrolyzing it, by means of a copper anode; as soon as 

 copper begins to be dissolved, the copper anode is removed, and its 

 place supplied with one of zinc ; after the action has continued for 



