(a) Single Winder Ploughing, complete equipment, consisting of one transformer wagon with 75 kva. transformer 13,0000 to 1100 volts, with choking coils, switchgear, watthour-meter, &c., designed for a continuous load. One winding wagon, including one 75 h.p. 1100 volt, 975 revolution three-phase motor, for a continuous load, with controller and switchgear, designed for a maximum pull of 4000 kgrms.; cable speed 1.6 to 1'1 metres per second; wagon speed, 14 to 21 kilometres per hour, with accessories. One anchor wagon; 600 metres of 1100 volt special flexible cable; one triple pole switch for trans mission pole. Price, cemplete, excluding plough, £1550. (b) Double Winder Ploughing, complete equipment,, consisting of two transformer wagons, each with 75 kva. transformers 10,000 to 750 volts, with choking coils, switchgear, watthour-meter, oil, &c., designed for an intermittent load. Two winding wagons, including two 75 h.p. 750 volt, 730 revolution three-phase motors, for intermittent load, with controllers and switchgear, each wagon designed for a maximum pull of 4000 kgrms. ; cable speed, 1.6 to og metres per second; wagon speed, 14 kilometres per hour. 600 metres of 750 volt flexible cable; one triple pole switch for transmission pole. Price, complete, excluding plough, £2000.

The only electric ploughing installation in this country (vide Electrical Review, Jan. 19, 1916) of which the author is aware was one carried out on a farm of 240 acres belonging to Mr. Chorlton, near Cotgrave, some eight or nine miles from Nottingham, by Messrs. E. O. Walker and Co., of Manchester. The soil was of heavy clay, which would be very difficult to plough by other than

mechanical means.

Threshing.-The driving of threshing machines formed one of the earliest applications of electricity in agricul ture. With the exception of electric ploughing, as regards motor capacity and power consumption, electric threshing occupies the highest place in purely agricultural work, and for this purpose motor wagons are largely used, as well as motor trucks and motor sledges.

With the building of long-distance central stations the application of the electric motor to threshing machinery has continued to increase, and it may be said that no farmer who has once tried electric threshing wishes to dispense with it if electric current current continues to be at his disposal.

Threshing in the field furnishes also one of the most important uses of the portable transformer in connection with agriculture. When a greater output is necessary, and when the distance of the work from the farmyard, and, therefore, from the fixed transformer which supplies current for lighting and power, is too great, the portable transformer finds a useful opening, and indeed it may be said that electric threshing plants obtain their full freedom of movement only when such a transformer is available. For this reason many threshing associations in Germany include a portable transformer in their threshing plant equipments, and thus open up the way for the general

* Reprinted by permission from the Journal of the Royal Society of Arts.

introduction of electric threshing throughout the country. The employment of a portable transformer enables the farmer to do his threshing at any desired place in the neighbourhood of an overhead high tension line. He thus saves time, as well as horses and workers, and avoids the wastage in carrying the corn for threshing to the yard, and afterwards removing the straw.

With regard to the actual application of the moters to threshing, reference may be made to Fig. 1, where a motor wagon is shown belted to a threshing machine in the field, the current being supplied through portable transformers from an overhead line. In some cases the threshing machine is provided with a "built-on" motor, and in this case, of course, the motor travels with the threshing machine and is not available for driving other machines.

The power taken for threshing depends upon the moisture present and the lengths of stalk. The following table based on actual measurements may be taken as reasonably reliable—

Rye
Wheat
Oats
Barley
Mixed grain

Killowatt hours per cent.

The horse-power of the motors required varies from 2 to 6 for threshing machines formerly worked by hand or by haulage animals.

Motors of 20-25 h.p. are used for larger machines with straw presses, and these have a current consumption of 10-12 kilowatts per hour and and an output of 20-30 cwt. of threshed corn.

The horse-power required for a given farm can be easily calculated from the number of acres, an estimate of the corn produced per acre, and the table given above for the units required per cwt.

The following particulars, which are largely based on letters from farmers and reports from public bodies, give some of the advantages of electric driving particularly in connection with threshing :

I. Low first cost and working costs as compared with steam threshing, especially when the horse power required is small or the working periods short, and particularly, of course, where a cheap supply of current can be obtained. The saving in energy and expense with the electric motor is shown by the fact that it can be stopped for short periods between work, when coal would have to be consumed in a steam traction engine to maintain steam.

2. The special preparation, such as the heating of the boiler in locomotives, the procuring of water, coal, &c., is not necessary with electric driving.

3. The motor is of small weight, occupies little space, and is, consequently, very portable and available for use at any particular place where it may be required.

4. The motor is adaptable to varied working conditions, for example, to change of weather, as during the rain when the form hands cannot work in the fields outside they can be withdrawn for the threshing, which it is understood in this case is carried on in the barn.

5. The simplicity of the control arrangements of the electric motor which are operated by the movement of a handle, handwheel, or something similar.

6. The fact that the efficiency of the motor is independent of its age. An electric motor also works at high efficiency even when the load it is taking is not as high as it is designed to take. This is not the case with steam driving, which practically consumes the same quantity of coal at light load, when driving very little, as it does on full load.

7. Great security against fire, and freedom from any danger of explosion.

8. The uniformity of rotation on the electric motor gives a cleaner threshing, consequently a smaller waste of current, and also a greater output in comparison with other kinds of driving.

NEW

FIG. 6.-PORTABLE MOTOR SLEDGE (Motor Protecting Cover removed).

FIG. 5.-FORTABLE MOTOR CRADLE WITH SELF CONTAINED GEAR REDUCTION.

FIG. 7.-PORTABLE MOTOR TRUCK (Motor Protecting Cover removed).

FIG. 9.-ELECTRIC PLOUGHING ON THE DOUBLE WINDER SYSTEM IN PROGRESS.

FIG. 8.- PORTABLE MOTOR WAGON, SHOWING CABLE DRUM.

FIG. 10.-ELECTRIC PLOUGHING ON THE SINGLE WINDER SYSTEM, SHOWING ANCHORAGE WAGON.

It has been shown by repeated measurements that the saleable corn resulting from electric drive amounts to from 1-1 per cent more than with the usual steam or other drive employed, due to the more uniform turning moment

of the electric motor.

It may also be added that there is no danger incurred by bringing the electric motor close to the fences or sheds, which is not the case with the steam locomotive, petrol engine, or gas engine, as the motor is fully enclosed, and in the larger sizes is carried with all its accessories in a small completely locked; wagon, which allows of easy transport and permits the motor to be placed as near as may be to fences, &c., and in any position in the sheds or yard. It can be placed in the barn itself, if necessary. In reply to a question when giving evidence before the Canadian Committee on Agriculture and Colonisation, a witness said, when referring to electric driving: "You can get a better quality of chaff, it absorbs the moisture from the grain when it is kept for a longer period before threshing; then again, your grain is a better product from leaving it longer in the head. In 1912, three-fourths of the grain in the country was heated because it was threshed ton soon, and most of it was harvested wet." (Report of Select Standing Committee on Agriculture and Colonisation, Canada. App. No. 2, 1914).

The cost of an equipment for electric threshing depends, of course, on the size of the threshing machine to be given, and on the accessories necessary. An approximate idea of the cost of the necessary motor wagon may be obtained from the figures already given; thus a motor wagon of 34 h.p. capacity, with accessories, should cost before the war approximately 2500 marks, and allowing 500 marks for the part cost of electrical conductors, &c., they would give a total first cost of 3000 marks exclusive of the cost of the transformer wagon if such were needed. The cost of this would, in any case, in part, have to be charged to other work.

General. For operations on the farm other than plough. ing and threshing, portable motors of the type already described are generally employed. Stationary motors are • also used where the work is of a more continuous nature.

An illustration of a permanent motor driving a model dairy in Canada is given in Fig. 14, the electricity in this case being supplied from the mains of the Ontario HydroElectric Commission.

The fellowing figures for power consumption on certain farming operations based on tests give some indication of the costs of performing these operations by electricity. Chaff Cutting.-A motor of from 2-5 b.p. will cut in an hour up to 20 cwt. of chaff with a current consumption of O'I to 0.3 kw. hours per cwt.

For purposes of comparison it may be said that it usually takes one man one hour to cut I cwt. of chaff, while two horses and a driver are capable of cutting 3 to 4 cwt. per hour.

Turnip Cutting.-The current consumption for this work varies from o'01 to 0'02 kw. hours per cwt.

Oat Crushing. The current consumption for oat crushing is about 0.25 kw. hours per cwt.

Milk Separating.-A motor of 1 h.p. can deal with an output of 2100 litres per hour with a current consumption for skimming, churning, and kneading the butter of 0.25 units per 100 litres.

In forming an idea of the probable cost of current to be consumed by a motor of given size on farm work, it should be remembered that an agricultural load is a very fluctuating one, and for general purposes it is usual to assume that a motor is on full load only during one-third of the working time, and that during the remaining twothirds of the working time it is only on half load, and it is found in practice that working on this basis gives a fairly good idea of the probable consumption.

In making a comparison between the working cost of driving by electric motor and by heat engines, in addition to the expenditure in coal, petrol, electric current, &c., allowance should be made for interest, depreciation,

maintenance, lubrication, and attention, and if these factors are taken into account it will generally be found that with the smaller motors up to, say, 20 b.p. electrical driving is cheaper than any other form of driving with current at the usual rates obtainable in country districts, whereas for outputs of above 20 b.p. the running costs of other forms of power begin to be competitive if the cost of electricity is excessive, particularly if the machines are in continuous service. The low first cost of electrical plant and the discontinuous service required for motive power in farm work are, however, very much in favour of electrical driving.

The following table gives approximate pre-war costs of the motor cradles, trucks, motor sledges, and motor wagons already described :—

Motor cradles up to 3 h.p., including 15 metres of flexible cable-without gear reductions ....

Ditto, with gear reduction Motor trucks or sledges from 2 to 6 h.p., including 20 metres of flexible cable

240-550 marks. 350-700 marks.

900-950 marks. 1400-1500 marks. 2200-2400 mares. 2900-3550 marks.

REPORT OF THE INTERNATIONAL COMMITTEE ON ATOMIC WEIGHTS FOR 1919-20.

THE last regular report of this Committee, apart from an annual recommendation to continue the use of the table

of atomic weights then presented, was published in 1916. The interruption in the series of reports was, of course, due to the world's war, which created difficulties of a serious kind among all international organisations. Cooperation with Germany became impossible, partly because of the difficulty of correspondence and partly because of the personal hostilities created by the conduct of the war. There was also an inevitable slackening of scientific activities, and this was well shown by the unusually small number of new researches in the field of atomic weights. Now that peace is in sight, it seems wise to resume the preparation of these reports, even though they may not be for some time quite so truly international as heretofore. The determination published since the preparation of our last report may now be summarised as follows:—

Hydrogen.-A very thorough investigation by Burt and Edgar on the volumetric composition of water has given the volume ratio of hydrogen to oxygen as 2.00288: 1, (Phil. Trans., 1916, 216 A, 393; this research was noted in the previous report for 1917; its review by Guye renders its repetition desirable here). From this value, taking the normal litre weights of oxygen and bydrogen as 142900 and 0.089873 grms. respectively, the atomic weight of hydrogen becomes 1'00772, or, rounded off, 10077. Guye (Fourn. Chim. Phys., 1917, xv., 208), from a discussion of Burt and Edgar's data, accepts this value as lying between the two extremes of 100767 and 100773. If, however, instead of trusting to the densities of the gases and their physical constants exclusively, we take into account the admirable researches of Morley, Noyes, and others, upon the synthesis and analysis of water, the most probable general mean for the atomic weight of hydrogen becomes 1'0078, which differs from the volumetric value by only 1/10000. (Computation by F. W. C). That is, the two distinct lines of attack upon the problem agree within the limits of actual uncertainty. For ordinary purposes the approximate value 1'008 is close enough. It must be remembered that the tables prepared by this com mittee are for the use, not so much for specialists, as for