Three types of mechanism whereby clay is flocculated by electrolytes, are discussed.

1. Normal or direct flocculation the mechanism of which is precisely that by which electrolytes coagulate electro-negative suspensoids. The isoelectric point theory of such flocculation is assumed in this paper. Experimental evidence is brought forward to show that iron and aluminium salts behave in this “normal” way.

2. Indirect flocculation which takes place whenever the electrolyte reacts with the clay and thereby brings into solution from the clay other substances which cause flocculation. The action of some neutral salts and of acids is regarded as being largely indirect.

3. Abnormal flocculation which is the result of a reaction between the added flocculant and the emulsoid surface of the clay particle. The action of calcium hydroxide is placed under this heading for reasons set forth in the earlier paper.

Because of its obvious bearing on important agricultural operations, the action of calcium hydroxide on clay is considered more fully. The following are the salient points of that consideration:

(i) Although it is reversible to carbonic acid the flocculation of clay by calcium hydroxide is not due to the formation of calcium carbonate. Several experimental results are set forth to show this, the chief is that barium and calcium hydroxides behave quite differently to carbonate and carbonic acid, and alike to clay.

(ii) The action of calcium hydroxide on clay is an action on an “emulsoid gel surface” and not an action on a sol present in gross amount.

(iii) The hydroxyl ion may perform at least two functions in its cooperation with the calcium ion in the flocculation of clay: (a) when added with or after the calcium ion it produces the alkalinity necessary for the reaction between calcium compounds and silica, etc., as discussed in the earlier paper; (b) when added before the calcium ion it not only produces this alkalinity but also peptizes the clay with the production of a greater amount of the emulsoid surface and a consequent increase in the rapidity of flocculation and the volume of the coagulum.

(iv) Critical mixtures of clay and silt—in which neither wholly dominates the system—can be obtained by decantation at an appropriate time during the sedimentation of soil suspensions. It is shown experimentally that when the clay of such mixtures is flocculated more rapidly than the silt, the silt then becomes dominant; and that when the silt is flocculated, more rapidly than the clay, the clay then becomes dominant.

(v) The different behaviour of “clay” and of “silt” to calcium hydroxide is not regarded as due to any essential difference in the structure cf these particles but as being determined by the ratio of the emulsoid surface to the core of the particle. In clay the surface dominates the system, in silt the core dominates the system.

(vi) In very low concentrations the hydroxyl ion appears to behave normally and to militate against the flocculation of clay by calcium salts.

(vii) Organic emulsoids may, in ordinary soils, be partly responsible for the anomalous action of calcium hydroxide on clay, but it is shown that calcium hydroxide exhibits that anomalous action on a deep subsoil clay containing no organic matter.

The feeding of concentrates after scalding with, boiling water and given to cows in winter in a sloppy condition at body temperature, increased the yield of milk by about 1 Ib. per head per day over the yield produced when the concentrates were fed in a dry state. The increase diminished with the advance in lactation.

The warm mashes produced a distinct laxative effect.

The animals took to the wet mashes better than to the dry meals.

When the concentrates were fed as dry meals in a ration containing 30 Ibs. roots with fodder and the drinking water taken from a trough in the yard, the coat of the animals got out of condition. With a change to the wet meal or when the drinking water was accessible in the byre, the coat regained its condition again.

An improved water supply did not appear to affect the milk yield.

The percentage of milk fat increased as the milk yield decreased.

Dairy equipment includes a boiler, therefore little, if any, additional capital outlay should be necessary for scalding the meals.

On an average 3·5 Ibs. of water were assimilated to 1 lb. of milk produced in a normal winter ration (see p. 89). The ratio varied with the feeding, the temperature and the period of lactation.

Drinking water and water consumed in the food amounted to about ten gallons daily, and of this between 50 and 60 per cent, was drinking water. The amount increased with an increase in the yield of milk and with a rise in the temperature. The smaller cows also consumed a relatively larger proportion of drinking water. From 25 to 30 per cent, of the total intake of water was contained in the mille.

The feeding of a large weight of roots (112 Ibs.) with meals and fodder caused the animals to scour badly. The health and the condition of the animal were also adversely affected. The milk yield which had shown a tendency to increase was converted into a definite decrease. There was an increase in the percentage of fat, although the total weight produced diminished. The fall in the milk yield was partly though not immediately arrested by a change to a moderate root ration and there was a decided increase in the percentage of, and in the total yield of, fat. Heavy root feeding would therefore appear to depress fat formation, though the supply of nutritive material in the food as judged by the usual method of calculation was not diminished.

The total weight of water consumed for 1 lb. of dry matter in the food amounted to 3·9 lbs. with the heavy and 3·3 lbs. with the moderate root ration. Some of the cows took water daily amounting on an average to between 5 and 6 per cent, of the total intake of water while on the heavy root ration.

Preliminary data relating to temperature and milk secretion were given.

Ayrshire cows were employed in the experiments.

The late Lieutenant H. A. Wyllie, B.Sc. was in charge of the 1913–14 experiment and Mr Hugh M. Young of the 1914–15 experiment. Determinations of the percentage of total solids in the milk were made by Mr Peter Caldwell.

Any additional expenditure incurred in carrying out these experiments was defrayed by the Board of Agriculture for Scotland.

1. The Sudan method for clay determination worked out by Dr Beam in 1911 has been critically examined and compared with the methods in general use in England and America.

2. The essential points of the method lie in (a) the use of sodium carbonate instead of ammonia as the deflocculating agent, and (b) the use of a camel-hair brush for puddling the clay. It differs from the English (and resembles the American) method in that no preliminary acid treatment is used, the height of the sedimentation column is 10 cms. and the time of subsidence 8 hours.

3. It can be applied to a sedimentation or centrifugal process: the results agree well with each other and with those obtained by the American method.

4. When modified by inclusion of acid treatment, by increasing the time of sedimentation from 8 to 24 hours and reducing the height of the column to 8·6 cms., the results agree well with those obtained by the English method.

5. Treatment with acid either in the preliminary operations or for deflocculating clay suspensions may lead to uncertainty in the results in some cases as it causes loss of “clay” by solution.

6. The Sudan sedimentation method can be carried out in about one-eighth the time required for the English method, and the centrifugal in about one-third the time required for the American. For general use the sedimentation method is preferred as requiring less attention.

During the past fifty years there have been many records of the damage done by this pest to wheat and rye on the continent.

The first record in this country is by Ormerod(i) in 1882 in wheat. She says “there is good reason for believing that it was present to a serious extent before.” Since that time numerous complaints of serious damage to wheat have been recorded in various parts of the country, but the eastern counties of England and parts of Scotland have suffered most and the intensity of the attack has varied enormously from season to season.

During the last decade the production of silage has, in various parts of the country, become a matter of considerable importance, and many scientific investigations in connection with this practice have been carried out. The bulk of this work has been directed towards the study of the changes undergone by the crop in the silo, together with the determination of the character and the amount of the losses which occur. Little or no attention has been given to the question of the digestibility of silage, although it is of obvious interest to determine how the digestibilities of its ingredients compare with those of the green crop from which it has been made. The investigation to be described in this communication is preliminary to one of larger scope, which will have for its object the comparison of the digestibilities of the green fodder, hay and silage of the oat and tare crop. A knowledge of these comparative data, when considered in conjunction with the available information regarding the losses sustained by the crop in the making of hay and silage, will enable the question of the relative economy of hay and silage production to be settled.

By means of a suitable fluid and a low temperature, it has been possible to keep mammalian spermatozoa in a condition of potential motility for 9 days.

1. The work presented in this paper covers a period of 13 years and gives the results secured, by means of cylinder experiments, in a comparative test of nitrogen in nitrate of soda, stable manure, and leguminous green manure crops, on eight types of soil, seven of which are Coastal Plain soils.

2. The work was carried out at the Experiment Station in galvanised iron cylinders similar to those used in the availability work which was started in 1898. 320 such cylinders were used, making it possible to run a four-year rotation on the eight types of soil with five different treatments for each type.

3. The five treatments are as follows: Series I—no fertiliser. Series II—minerals only (phosphoric acid and potash). Series III—minerals and leguminous green manure crops to supply nitrogen for the four main crops. Series IV—minerals and stable manure.

All cylinders receive liberal applications of ground limestone every five years.

4. The rotation consists of rye, corn, potatoes and oats, all grown every year on the eight soils.

Crops are harvested at or near maturity, dry weights recorded, and samples prepared and nitrogen determinations made in duplicate.

5. Under all of the treatments the largest crops were obtained during the first two or three years of the period. From the point of maximum yield which in most cases occurred within the first three years, there has been a gradual decline in yields, both of total dry matter and total nitrogen.

This decline, however, is not without some exceptions.

Without exception the average yields for the 13 years are less than the average for the first seven years.

6. Of the eight types of soil used Quinton sandy loam has consistently given the largest crops and the largest nitrogen return, followed closely by Penn loam. Norfolk sand has likewise consistently given the lowest returns.

Windsor sand has shown a remarkable response to the green manure treatment.

7. Of the five different treatments the green manure series has given the highest average returns on all the soils, although in a few cases scattered through the 13 years (and for the majority of the soil types during the first two years) the nitrate of soda series gave the largest yield. In a very few cases the yield on the stable manure series has exceeded that of the green manure series.

The average yield of the nitrate series stands between the green manure and stable manure series.

8. It has thus been shown that for a period of 13 years nitrogen supplied by leguminous green manure crops, grown between the main crops of the rotation, has been more effective in crop production than 15 tons of manure every two years, while at the same time the nitrogen content of the soil of the green manure series was maintained, for a period of five years at least, on a level with that of the stable manure series.

9. It has also been shown that the green manure series yielded larger crops than the nitrate of soda series (160 lb. of nitrate per acre annually), while at the same time the nitrogen content of the soils of the former was maintained at a higher level than that of the latter.

10. It is pointed out that it may be possible to maintain crop yields at a rather high level, even when the total nitrogen content of the soil is not kept at quite so high a level as was found in the original soil. Under such conditions, however, a constant turnover of readily available nitrogen is necessary.