§ 1. In Part I. (vol. IV. pp. 1—24) it was shown that the intrinsic permeability of a soil when measured with water was less than when measured with air as the experimental fluid, and that the ratio of the two values varied with the amount of colloidal matter present. It was desirable to determine accurately whether the values would be identical for soils composed of pure sand or other uniform and non-colloidal particles.

The experiments of Russell and Hutchinson1 have shown that the micro-organic population of ordinary soils is not working at a maximum efficiency; there exists a biological factor, provisionally identified with the soil protozoa, detrimental to bacteria and limiting their numbers and activities. It follows that any change in the conditions of the soil that is more favourable to the harmful organisms than to the bacteria will disturb the normal equilibrium between these two sets of organisms and lead to a relative reduction in bacterial numbers and activity. We shall therefore expect to find that causes not in themselves harmful to bacteria may bring about a reduction of bacteria through favouring the development of the detrimental factor.

In a recent number of this Journal, T. B. Wood and F. J. M. Stratton have discussed the probable error of field and feeding experiments, but in the latter case their investigations included only cattle and sheep.

The following work was undertaken as a necessary preliminary to a series of pig feeding experiments which are in contemplation. It is published at once in the hope that the results obtained may be of use to others who may be engaged in planning similar feeding trials.

It is shown that whereas the platinum chloride method of estimation is uncertain and liable to give varying results, the perchlorate method described is at once more simple in manipulation and more uniform and exact in its results. An improvement has been introduced which consists in washing the perchlorate precipitate with 95% alcohol saturated with potassium perchlorate by means of which any error due to the solubility of the precipitate is obviated. This is of importance when dealing with small quantities of precipitate. The following other advantages may here be enumerated:

The present paper deals with the results of an investigation on a serious and common disorder of cider, generally known as cider sickness. The account here given is concerned with its characteristic features, its cause, and, as far as present knowledge permits, methods for its prevention. The disorder is due to the action of a bacterium. It is proposed to give a detailed account of the organism and its chemical activities in a supplementary paper.

Previous investigations in this laboratory have shown that partial sterilisation of soil leads to increased productiveness. In attempting to apply this method on the large scale two courses were open. The more obvious was to seek for methods cheap enough for use in the field, and then to conduct a number of field trials to determine which was the best; this was almost certain to prove a tedious and expensive business and would not necessarily lead to a successful issue. The alternative plan, and the one we adopted, was to find classes of growers who could afford to use our present methods of partial sterilisation and who would be willing to do so. However restricted their number of crops might be we knew that the cost of the process must fall once it was applied in commercial growing, so that the range over which it was applicable would soon begin to widen; a further advantage was that from the outset we should be gaining experience of the working of partial sterilisation in practice. Fortunately we met with a large tomato and cucumber grower in the Waltham Cross district who put us in touch with the class of growers we wanted: in this way we came across the problem of sickness in glasshouse soils which forms the subject of the present communication.