in the form of colloid sols or in the state of solution and its deposition at lower depths in the soil where it acts as the cementing material to the normal soil particles.

The present paper is concerned with the latter kind of pan.

Pan formation of this nature is almost always confined to soils composed for the most part of quartz sand, and as the normal drainage in such soils is rapid, the existence of the impervious layer is very marked. The pan layer, which occurs at a

depth of 5-60 cms., varies in colour from a dark brown to a reddish yellow. The subsoil appears to be the ordinary and typical sand of the locality, unaltered in any way. The zone immediately above the pan is remarkable in the fact that it is almost free of iron and aluminium, and hence has a bleached appearance. The surface soil is usually rich in acid humus, and is almost completely free from calcium carbonate. The analytical figures for two typical samples of pan-bearing soils are given below:

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The main facts, therefore, in connection with the presence of pans in soils are the following:

(1) The formation of pans generally in sandy soils of open texture.

(2) A considerable accumulation of organic matter in the surface soil.

(3) Concentration of iron and aluminium hydroxides in the pan layer and other lowér layers.

(4) The almost complete absence of calcium carbonate in the surface soil.

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Various theories have from time to time been advanced to explain this phenomenon from the chemical point of view, such the alternate reduction and oxidation of iron humates, but an exhaustive examination of these (Morison and Sothers, loc. cit., Stremme, Kolloid Zeitsch., 1917, XX., 161) shows that the most probable explanation of the phenomenon lies in the colloidal properties of soils.

We have already mentioned the curious. phenomenon of banded structure of the precipitate of silver chromate formed by the interaction of silver nitrate solution with potassium chromate in gelatin gel. It has been found that various other media, such as agar-agar and silicic acid gels also behave in the same way as gelatin. But the action of gels in bringing about periodic precipitation is specific. For example, silver chromate forms rings in gelatin, but not in agar-agar, while lead iodide gives these in the latter but not in the former. We have observed that ferric hydroxide gets precipitated in rings when a soluble ferric salt is present in silicic acid gel, and gets slowly

acted upon by an alkali from above. cently, Bhatnagar and Mathur (Kolloid Zeit., 1922, XXX., 368-71) have been successful in preparing a number of different kinds of periodic precipitates in this gel.

No satisfactory explanation has yet been forthcoming for this interesting phenomenon, but as shown by Chatterji and Dhar (Kolloid Zeitsch., 1922 XXXI.), peptisation plays an important part in the formation of banded precipitates. In almost all cases where banded precipitates are formed, the phenomenon of peptisation has also been noticed. The facts observed in connection with the formation of these banded precipitates may be summarised as follows:

(1) The phenomenon takes place in a gel in which one of the reacting substances is dispersed.

(2) The spaces above and between the rings are almost entirely free from the reacting substances.

(3) Complex organic matters of a colloidal nature help the taking place of the phenomenon.

If we compare the above facts with those that have been set forth before in the case of pan formation, the similarity becomes at once obvious. The formation of pans in soils is in all probability another example of periodic precipitation on a large scale in nature. At first the soluble salts of iron and aluminium are present in a state of solution throughout the mass of a medium of silicic acid gel. The gel is, of course, formed from the silicic acid sol resulting from the gradual disintegration of rocks by

In

rain water and their colloidal dispersion. The alkali, naturally present in the soil, or ammonia formed from the organic matter, begins to react with the salts of iron and aluminium producing the insoluble hydroxides, which get precipitated in rings or narrow bands in the silicic acid medium. course of time the silicic acid gel dries up and gives rise to the typical open texture sandy soil, consisting of quartz grains, the zones of ferric and aluminic hydroxide precipitates forming hard, compact masses, commonly known as " pan.

If this view about the formation of pans in soils is more or less correct, we can easily assign reasons for a number of facts which have been observed in connection with this phenomenon, and which have previously been overlooked. Thus if we scrutinise the analytical figures given above for the pan-bearing soil, it would be found that the iron and aluminium contents of the soil below the pan are much higher than those above, so that there seems as if there is not one layer of pan, but several layers of it close to one another. This is what is expected from the point of view of periodic precipitation. Again, pan-bearing soils are rich in organic matter, and as has been said before, the presence of this considerably enhances the peptising power of the medium and helps in the subsequent formation of banded precipitates. The almost entire absence of calcium carbonate from the soil cannot at present be more satisfactorily accounted for, beyond the fact that the periodic precipitation of substances specific in nature and that calcium hydroxide or carbonate does not bring about the preliminary peptisation of iron or aluminium hydroxides in silicic acid gel.

Technological Institute,
Cawnpore (India).

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FARMING METHODS IN NORTHERN MANCHURIA.

(Journal of the Royal Society of Arts, July 20, 1923.)

Northern Manchuria is pre-eminently a country of small landowners. The landowner himself works his fields in the majority of cases, but the larger landowners often turn their farms over to tenants.

The division of the land into small parcels and the low purchasing power of the individual farmer have been serious draw

backs to the introduction of modern farming machinery, and Chinese conservatism and loyalty to traditions have also been opposed to new methods of farming. In a district covering an area of approximately 250,000 square miles there are, according to information furnished by one of the large dealers in agricultural machinery, only about 300 ploughs of the American type and some 500 German Sack ploughs. There are only 300 disc harrows, and very few mowers, reapers, and self-binders. Even these are not Chinese ned, but belong to Russian farmers who have settled in the zone of the Chinese Eastern Railway.

In Northern Manchuria, according to a report prepared in the American Consulate at Harbin, the land is very carefully worked, great attention being paid to fertilisation. The land is ploughed in paranel ridges and furrows. The soil is worked twice, which enables the roots to draw moisture from the night air, even in time of drought.

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The plough used is very primitive. Into wooden frame is set a spade-shaped ploughshare, which is clamped to the bent wooden lever or beam. The other end of this lever serves as a handle, and at the The middle of it is fastened a grader. ploughshare is held in almost a perpendicular position to the surface of the land and tears it effectively. This plough is usually drawn by two animals (horses, mules, or oxen), and is attended by two labourers, one of whom guides the plough and the other the animals. It is transported to and from the field on a special wooden drag.

There are two methods of ploughing the soil. Either the ploughshare follows the ridge, and where last year there was a ridge there will be a furrow this year, or the ploughshare follows the furrow, and where last year there was a furrow there will also be a furrow this year.

Sowing or seeding is seldom performed by hand, the use of a "chan hu lu" being more popular. This is a dried pumpkin, which has an opening made in the narrow end. The pumpkin is filled with seeds and the opening is then closed with a cork, into which is fitted either a reed or some kind of piping in such manner that the seeds will scatter if the instrument is slightly tipped and lightly tapped with the hand. One workman, carrying the "chan hu lu," walks along the furrow, and tapping the pumpkin with his right hand, he scatters

the seed so that they fall on the ridges. Another man, walking along the ridge, stamps the seeds down with his feet. Behind them follows a third man, with a horse which pulls a small stone roller. This roller follows the two ridges. On the new ridge it levels out the crest, and on the other it smooths out the tracks of the second labourer's feet and covers the seeds with earth.

When weeds begin to appear the Chinese farmer once more follows along the furrows with his plough, deepening them by half a foot so as to surround the sprouts with 'fresh earth. When the sprouts have reached considerable height the plough is again used for bringing the deeper roots closer to the surface, thus enabling them to absorb more moisture from the air. By this process weeds are also destroyed between the ridges. On the ridges themselves weeding is done by means of hoes.

For the harvest of cereals the Chinese farmer uses a special scythe, which is similar to the American scythe but of smaller dimensions. Very few Chinese farmers in Northern Manchuria are familiar with flails. In threshing, the plants are placed in a circle, with heads toward the centre, and over these is drawn by animals a heavy stone roller. Before the kaoliang is threshed, however, the heads are cut off from the stalks to prevent these being spoiled by the roller, for the kaoliang stalk plays an important rôle on the farm, inas much as it is used for roofing, fencing, fuel, and many other purposes. The roller process is continued until all the grains have been removed. Winnowing is done with shovels and old-fashioned hand sifters.

The threshed and cleaned grain is stored either in pits or in specially constructed cylindrical silos, covered with a conical roof. These silos vary in size according to the requirements of the individual farm. They are built of poles, which are plaited with dry twigs, the whole structure being plastered inside and outside with a composition of clay and straw cuttings. It is divided into two or three compartments for the different kinds of cereal. Besides these silos the Chinese employ so-called "chantze." These resemble wells and are made of boards.

The threshed grain is ready for the market and for the feeding of cattle. For preparing human food, however, it is necessary that the hulls be removed. This is done by the " chantze -a round, sta

"

tionary, horizontal millstone, upon which rotates a stone cylinder with a rough surface. This cylinder is usually moved by small donkeys.

The Chinese plough is particularly unsuitable for breaking new ground, and this is one reason why the Chinese farmer is reluctant to take up virgin land. Some years ago the Government conceived the idea of ploughing up large tracts of land in order to sell them to immigrants from the south. It is believed the plan fell through because of some unfortunate financial manipulation in connection with the purchase of machinery. It seems, nevertheless, that this idea may be revived by some enterprising manufacturer, with a view of introducing modern farming machinery on a large scale through the agents of the Government. There appears to be a tendency at the present time to encourage immigration into the Nonni Valley and other parts of Heilungchiang Province.

The Chinese Eastern Railway, which maintains two agricultural experiment stations in the district-one of 300 acres at Station Anda, and one of 250 acres at Old Harbin, together with an experimental farm of 700 acres at Station Echo-appropriated 60,000 gold roubles for farming experiments during the year. The representative of a large American firm has been conducting tractor trials on these grounds, and they are generally reported to be exceptionally satisfactory. Two tractors are being experimented with-one pulling twobottom ploughs and the other pulling fourbottom ploughs. This representative is of the opinion that the future of these tractors in Northern Manchuria is most encouraging.

The market in Northern Manchuria appears to be worthy of study on the part of manufacturers of agricultural implements, especially the smaller type of implements, such as ploughs, cultivators, seeders, threshers, and fanning mills.

THE PREPARATION OF STIBINE FROM ALLOYS.

BY EDWARD J. WEEKS, M.Sc., F.C.S.

Various workers have given the percentage composition of alloys of zinc and antimony best suited for the preparation of stibine, but if these results are summarised

In 1889 Berthelot and P. Petit (loc. cit.) stated that no stibine is obtained unless 5 atoms of zinc are present to one atom of antimony. This gives 1 part by weight of antimony to 2.8 parts of zinc.

It is noticed from the above that A. Stock and W. Doht give as the best alloy 2.5 parts of zine to 1 part of antimony, or 1.35 atoms of zinc to 1 atom of antimony. This does not agree with the statement by Berthelot and P. Petit, and indeed these workers themselves state that stibine may be prepared from an alloy of 2 parts of zinc to 1 of antimony, or 1.09 atoms of zinc to 1 atom of antimony, an experiment which does not agree with their own statement.

We must, therefore, conclude that there is no actual best composition of the zinc, antimony alloy for the preparation of stibine, but that the same amount of stibine may be obtained from any alloy of composition varying from 1 part of zinc to 4 parts of zinc to 1 of antimony.

Sir John Cass Institute, Jewry Street. 2/8/23.

E. A. BOLTON, M.Sc., Birmingham, The Cause of Red Stains on Sheet Brass.

H. W. BROWNSDON, M.Sc., PH.D., F.I.C. (Member of Council), Note on Brinell Hardness Numbers.

H. I. COE, M.Sc., Swansea, The Behaviour of Metals under Compressive Stresses.

HIKOZO ENDO (Sendai, Japan), On the Measurement of the Change of Volume in Metals during Solidification.

ULICK R. EVANS, M.A., Cambridge, The Electrochemical Character of Corrosion.

MARIE L. V. GAYLER, M.Sc., Teddington, The Constitution and Age-Hardening of the Quarternary Alloys of Aluminium, Copper, Magnesium, and Magnesium Silicide.

D. HANSON, D.Sc., C. MARYATT, B.Sc., and GRACE W. FORD, B.Sc., Teddington, Investigation of the Effects of Impurities on Copper. Part I.-The Effect of Oxygen on Copper.

DOUGLAS H. INGALL, M.Sc., Wednesbury, Experiments with some Copper Wire: Cohesion a Function of both Temperature and Cold-work.

A. H. MUNDEY and C. C. BISSETT, B.A., B.Sc., B.MET., London, Note on The Effect of Small Quantities of Nickel upon High-Grade Bearing Metal.

A. H. MUNDEY and JOHN CARTLAND, M.C., M.Sc., London, Stereotyping.

HUGH O'NEILL, M.MET., Manchester, Hardness Tests on Crystals of Aluminium.

ALBERT M. PORTEVIN, Paris, and PIERRE CHEVENARD, Imphy, A Dilatometric Study of the Transformations and Thermal Treatment of Light Alloys of Aluminium.

R. C. READER, PH.D., M.Sc.. Birmingham, Note on Effects of Rate of Cooling on the Density and Composition of Metals and Alloys.

E. L. RHEAD, M.Sc.TECH., and J. D. HANNAH, Manchester, Crystallisation Effect on Galvanised Iron Sheets.

PROFESSOR P. SOLDAU, Petrograd, Russia, Equilibrium in the System Gold-Zinc (based on Investigations of Electrical Conductivity at High Temperatures).

Full particulars can be obtained from the Secretary, G. Shaw Scott, M.Sc., 36, Victoria Street, London, S.W.1.

THE BRITISH CHEMICAL AND DYESTUFFS TRADERS 'ASSOCIATION.

The Committee of the above Association have forwarded a memorandum from H.M. Treasury, containing proposals that it is suggested may lead to increased shipments. of chemicals from this country-as the matter seems to us to be of special importance, we reproduce it in full below:

[COPY.]

Memorandum from The British Chemical and Dyestuffs Traders' Association on the method of payment of duties under The Safeguarding of Industries Act, 1921Part I.

Importers of goods scheduled under Part I. of The Safeguarding of Industries Act, 1921, have to pay the duty of 33 per cent. at the time the goods are landed and cleared at H.M. Customs.

This procedure, it is understood, is governed by Section 39 of the Customs Consolidation Act, 1876, whereby H.M. Treasury are given power to decide whether goods liable to import duties shall be allowed to be bonded or not.

The Treasury Order in respect of The Safeguarding of Industries Act, 1921, stipulated that the duties should be paid at the time of landing and clearance of the goods at H.M. Customs.

During the period this Act has been in orce it has been found that the present method of payment of duties as outlined above is, in many ways, having a detrimental effect on the commerce of this country. The following points are submitted in support of this view:

1.-Prior to the introduction of The Safeguarding of Industries Act and the import duties it entails, merchant importers were in the habit of holding as stocks bulk supplies of goods, and were thus enabled to meet both home and overseas demands

without delay. The re-exportation aspect

was then of very considerable importance, it being estimated that quite half the voiume of imports now liable to Key Industry duty were, when previously allowed free import, disposed of by way of re-export sales. Careful and exhaustive enquiry has been made as to what effect the payment of import duties under the Act has had on this important branch of the chemical trade, and it has been found that:

(a) The difficulties and uncertainty of obtaining "drawbacks" of duties paid at the time of importation make it impracticable for merchants to compete in overseas markets. For instance, unless a merchant holding stocks of goods on which duty under this Act has been paid can ascertain definitely and quickly whether he can recover such duty upon re-exportation, he is unable to arrive at his selling price, and is thus prevented from competing for overseas business. It is certain that if he does not allow for a "drawback" his price to the foreigner would not be competitive.

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(b) That on account of this position the volume of re-exports of goods liable to Key Industry duty has fallen away in a very deplorable manner, and merchants are tinually complaining that they have, and still are, losing such business, and state that it is largely due to the disadvantages arising out of the present method of collection of duties levied under the Safeguarding of Industries Act, 1921, Part I.

(c) Some firms, in an endeavour to overcome this barrier to re-export trade, are now holding stocks at Continental ports and This must meeting demands in that way. entail loss of freights to the shipping interests of this country; loss of employment at the docks, in warehouses, and in various other directions. It has been found that in this way only is it possible and practicable for merchants in this country to hope to compete successfully in overseas markets.

(d) Claims for drawbacks usually take a considerable time to settle, and in many instances where the goods in question have, since their importation, changed hands one or more times, it has been found almost impossible to satisfy H.M. Customs as to their identity. While the merchant is attempting to overcome these difficulties the overseas business is lost.

2. As regards sales of dutiable goods in this country, merchants, in order to carry on their business as economically as possible and to fulfil their function as distributors, are in the habit of importing in bulk