1. The free air in the pores of the soil to a depth of 6 inches is very similar in composition to the atmospheric air but it differs in two respects:

(a) It contains more CO2 and correspondingly less oxygen, the average in 100 volumes being 0–25 volume CO2 and 20–6 of oxygen against 0–03 volume CO2. and 20–96 oxygen in atmospheric air.

(b) It shows greater fluctuations in composition.

Usually the sum of the CO2 and oxygen is only slightly less than in atmospheric air but at periods when nitrates rapidly increase there is a perceptible falling off of oxygen, and a still greater one in waterlogged soils.

The work discussed in this paper is a continuation of that described in a previous communication to the Centralblatt für Bakteriologie. Unfortunately it has been found impossible to bring all the problems taken up to a satisfactory conclusion in the time available. And as, owing to unforeseen circumstances it is necessary, for the present at least, to leave this subject, the results so far as they have been arrived at are brought together in this publication and the lines on which it had been intended to work are indicated. It is hoped, however, that an opportunity of continuing this work on the soil Protozoa may present itself at some future date.

The experimental results described in the two parts of the paper may be summarised thus:

Part I. Lime Requirements for Sterilisation Purposes.

(1) The capacity to produce partial sterilisation effects is a property belonging to calcium oxide (caustic lime), but not to calcium carbonate (chalk, limestone, marl, etc.).

(2) The amount of lime necessary to produce specific effects in different soils has been found to vary greatly and it is not possible to make any general recommendations.

During the last three or four years, the protozoa of the soil have been the object of a considerable degree of interest, and investigations into their occurrence and importance have been made by workers here and elsewhere. The aim of the present paper is to indicate what we know of the life of the protozoa in the soil, and to furnish descriptions of certain methods which have been found useful in work on this subject.

Owing to the rapid rise in the price of linseed and linseed products during recent years, the question has arisen as to whether the farmer can grow linseed, for home consumption, at a smaller cost than he can buy it for under existing conditions. This question involves considerations as to which of the several kinds of linseed would be the most profitable to grow, and it becomes necessary to consider not only the agricultural requirements of the crop, but also the fact that the value of this crop is largely, if not entirely, determined by the quantity of oil produced per acre.