§ 34. 1. The permeability and capillarity constants of soil have been defined.

2. The movements of air and water through three types of soil have been measured and shewn to conform to equations connecting the rate of motion with the above constants.

3. It is suggested that the measurement of S, Pα, Pω and K is of more importance than, and should replace, the determination of the sizes of the soil particles as in the usual “mechanical analysis” of soils.

In conclusion, we have to acknowledge our indebtedness to Professors T. R. Lyle and R. J. A. Barnard for valuable advice and suggestions and to the Victorian Government for financial assistance towards the expenses of this research.

The following pages contain a summary of investigations and observations that have been made during the years 1906—1910, in part at the Manor Farm, Garforth (Experimental Farm of the University of Leeds and Yorkshire Council for Agricultural Education) and also in various parts of the city of Leeds.

Throughout the whole history of agricultural chemistry attention has been fixed upon. the ammonia in the atmosphere as a possible source of the nitrogen of vegetation, and without reviewing the early controversy that centred round Liebig, we may agree that the dispute was largely due to the exaggerated opinions then prevailing as to the amount of ammonia in the atmosphere. The most trustworthy determinations are the long series that have been carried out by Lévy at Montsouris, and they agree with other determinations by Ville, Schloesing and Muntz and Aubin. showing only from ·01 to ·02 of nitrogen as ammonia per million of air even in Paris, with a still smaller proportion in the air of the country.

The fungicidal properties of the insoluble copper compounds, present in Bordeaux mixtures, have long been known, and it is an important point to ascertain the precise manner in which the poisonous action is exerted. A variety of theories have been put forward, but the matter cannot be regarded as settled. It has been generally accepted that, in order to account for the fungicidal action, it is necessary to look for some means by which the insoluble copper in Bordeaux mixture is rendered soluble when the material is sprayed on to foliage. Atmospheric carbon dioxide has frequently been suggested as the most important agent by which this is effected, and recently this view has been urged by Mr S. U. Pickering, F.R.S., who has also investigated in detail, the chemical nature of the compounds found in Bordeaux mixtures.

The mixture of copper sulphate and lime universally known as Bordeaux mixture has been in common use as a fungicide in many countries for some time; but it is still uncertain by what means such a mixture, containing no soluble copper, is effective. It has undoubtedly a physiological effect upon plants on to which it is sprayed, and may increase their powers of resistance to the attack of parasites; but in addition to this, there appears to be a direct fungicidal action which requires explanation.

History has little of note to relate regarding cereal rusts in South Africa. G. W. Thompson (1) in his Travels and Adventures in South Africa informs us that the wheat crops during 1708—1710 were severely attacked by rust. Theal (2) nevertheless maintains that rust in wheat was not known in the country before the year 1727, when the epidemic was so bad that the crops were almost a complete failure, although he states that rust in rye had been known before 1727. The year 1820, however, is reported as one notorious for the severity of the rust attack.