Though doubtless the phosphoric acid would be largely present as phosphate of iron, and therefore not readily available, it might form a cheap and useful manure.

The night soil of some of the compounds on the Rand is treated so as to render it odourless by heat. The so-called "ash" left was found to contain :

If the product can be produced in large quantities, and equal to the sample, it should find a ready sale as a fertiliser.

From the above account it will be seen that the natural sources of phosphates in this Colony are limited, and in many instances it may be necessary to purchase imported materials. Superphosphates are well suited for such of our soils as contain, say, one per cent. or more of lime as carbonate, but with the great majority of our soils, poor as they are in lime, basic slag or "Thomas phosphate" will probably be the best form of phosphatic manure.

3.-LIME.

Fortunately, of this important substance, the Colony has large natural resources. Quantities of limestones, some of great purity, exist in many districts, and though I believe that it is true that a large proportion of the lime commerciably obtainable is of poor quality, being badly burnt and containing much insoluble matter and magnesia, this could be easily remedied by proper management, and the choice of suitable limestone.

We have examined many specimens of limestones, and among them were some of excellent quality, capable, if properly burnt, of yielding lime admirably suited for agricultural purposes.

As typical examples of such pure limestones, though it is, perhaps, more correct to describe some of them as calcite, but of which large deposits are said to be available, I may quote the following analyses :

As examples of the commercial lime obtainable, the following may be cited:

:

"Blue lime." "Blue lime." Good white lime.

Total lime

55.85

In some districts limestones do not occur, and I have had correspondence with farmers who were anxious to procure lime for agricultural purposes locally, so as to avoid the cost of transport from a distance. Several substances suspected to be rich in lime have been sent to me, but on examination these minerals have been found to be almost free from that constituent.

The ashes of certain trees have been found to be very rich in lime, and might be used for agricultural purposes when available. Thus a tree from Mozambique was found to yield about 6 per cent. of ash, of which about two-thirds consisted of lime. Another sample, the ash of a tree known as " Mopani," growing in the Tati Concessions country, was found to contain over 55 per cent. of lime, a considerable portion of which existed as carbonate.

4.-POTASH.

As already stated, it is on comparatively few of our soils that potash manures are required.

Probably wood ashes are the most readily available natural source of potash, especially the ash of twigs, brushwood, etc.

Should imported manures be used, preference should be given to sulphate of potash. On no account is it advisable to use the lowerpriced Kainite, which is open to the objections of involving a much. greater cost in transport for the same quantity of potash, and to being contaminated with large quantities of saline matter, which is not only useless, but may prove very harmful.

In conclusion, I would emphasise the importance of utilising as fully as possible the natural manurial resources of the country, and thus avoiding the expense which is involved in the purchase of imported manures. Indeed, so high are the prices of the latter, when the cost of transport is included, that it is often a matter of difficulty to know whether one is justified in recommending their use, and whether the undoubted increase in yield which would follow their application would pay for their cost.

Greater attention should be paid by the farmers to the preservation and restoration to the land, of all the waste products of the farm, the use of green manuring, and all means by which the muchneeded combined nitrogen, phosphates, and lime may be conveyed to

the soil.

OTHER EARTH MOVEMENTS.

BY JOHN MILNE, F.R.S.

At the present time the greatest seismic activity in the African Continent is to be found in the high lands of Algeria and in the vicinity of the Great Lakes, and Abyssinia. If from the former of these districts we travel Eastwards in the direction of Tunis, or Westwards through Morocco and turn Southwards down the Western side of the Continent, the activity rapidly decreases. A similar decrement is met with if from the central region we go Northwards down the Nile Valley or Southwards towards Cape Colony. Not only is the frequency small, but the shocks themselves are insignificant. They are local in character, and probably represent slight adjustments on lines of existing faults. For ten years at least Africa has not produced a single world-shaking earthquake, the inference from which is that during this period no large fault has been created. If, however, we regard the African Continent as a mass which extends Eastwards to the floor of the Indian Ocean, we find that the sites of several megaseismic efforts have been traced to this submerged frontier. From the changes which have taken place in soundings after a large earthquake which has originated beneath a sea or ocean, but more particularly from measurements made on land, when it has been found that valleys have been contracted, and the lengths of trigonometrical lines have been altered and from other observations, the conclusion arrived at is that a world-shaking earthquake originates from the faulting, shattering, and the displacement of an area only to be measured by many thousands of square miles. If we had a knowledge of the depth to which the faulting extends, a cubic measurement might be made of the magnitude of these molar displacements. Inasmuch as they transmit sufficient energy through the crust of our earth to create movements which may be recorded at the antipodes of their origin, it seems probable that the displacement downwards extends to a considerable depth. If we regard the crust of our world as a layer of materials which conveys elastic vibrations at about the same rate as they are conveyed by the rocks we see, then seismological investigations indicate that this covering is less than 30 miles in thickness. In relation to the area which is displaced, fracturing to this depth, or, at least, to a large fraction of the same, might be compared to the formation of the tiny cracks we sometimes see in the varnish covering an ordinary globe. The origins of the displacements along the line of the Mozambique synclinal have apparently been too far from the African coast for the resultant vibrations to be felt, but they have been recorded in very distant countries. At the present time in Africa the British Association type of seismograph, which is not adapted to record local earthquakes which can be felt, but only to record unfelt teleseismic motion, is only to be found at Cape Town and Cairo. Forty other similar instruments are installed in Europe, Asia, America, and Australia. Capt. H. E. Lyons, R.E., of the Egyptian Survey Department, now proposes to establish observing stations at Khartoum and Lake Victoria. The

object of the latter installation is not simply to make a register of world-shaking earthquakes, but to obtain a continuous record of changes in level. The water of Lake Victoria fluctuates in its height, and it is suspected that this may possibly be due to rock folding. If this is the case, then a seismograph, which can be adjusted to record small changes in level, may possibly yield information connected with the water supply of Egypt. Between Victoria and Cape Town there is a stretch of some 2,000 miles, in which, if two or more stations were established, records would be obtained of immense value to the seismic survey of the world which is now in progress.

Not only would they be of value as a means of extending our knowledge respecting the nature of the interior of the planet on which we live, but from time to time seismograms would yield information of immediate practical value to South African communities. Certain colonies have established seismographs because they furnish information as to the cause of a certain class of cable interruption. Cables may cease to work in consequence of the operations of an enemy, in consequence of sub-oceanic seismic disturbances, and for other reasons. A community that can be assured of the reason why its communications with distant places have suddenly ceased, should certainly be less liable to anxiety and alarm than one without similar information.

For the East Coast of Africa in 12 years I find that out of 19 cable interruptions II of these have corresponded with unfelt earthquakes which were recorded at many stations in different parts of the world.

It cannot be said definitely that these earthquakes were the cause of the interruptions, but the fact that both occurred on the same days, and that it has so frequently happened that cables have been parted by sub-oceanic convulsions, makes it appear likely that in certain instances, at least, we may be dealing with causes and their effects.

On Jan. 31st of this year an earthquake off the Coast of Columbia, the effects of which found responses in the W. Indies, was responsible for the parting of 8 or 9 cables.

When one or two more earthquake observing stations have been established in Africa, the origins of these sub-oceanic catastrophes will be localized, and their relationship to the cable interruptions will be better understood.

Seismographs have been established at Potsdam and at several magnetic observatories in the United States, mainly because the records they yield throw light upon perturbations noted in certain. magnetograms. At other observatories records of unfelt movements of the ground have explained accelerations and retardations in timekeepers, sudden displacements on barograms, and unusual movements of electrometers, the assayers' balance, and other instruments. In addition to changes of level, which are only appreciable after long intervals of time, a horizontal pendulum readily records changes which take place with comparative rapidity. Diurnal changes in level, which are chiefly noticeable in fine weather, have been recorded

at a depth of 19 feet in sandstone. On the opposite sides of two valleys where instruments have been established, it is found that these daily movements take place simultaneously, but in opposite directions. During the day we may picture a valley opening, and at night as closing.

Bearing in mind that these diurnal movements are only marked on bright, sunny days, and are practically absent in dull, wet weather, we may seek for their explanation either as a general expansion of the ground under the influence of sun heat, or to a diurnal loading and unloading of a valley bottom relatively to that which takes place upon its sides.

The fact that these deflections of the pendulum may be observed in cellars and chambers excavated in rock where temperature is practically constant, precludes the idea that they are due to any local heating of the foundation on which the instrument may be installed. It, however, does not preclude the idea that there may be a general superficial warping of a district as an effect of solar radiation. It is, however, remarkable that this action should extend to the depths at which it has been observed.

That valley beds convey more load at night than they do during the day is suggested by various observations. Engineers have shewn that under normal conditions certain streams carry the most water at night time. This is also true of certain drains and wells. The causes leading to these conditions may be various. A nocturnal increase in the flow of sub-surface water may be attributed to the expansion of air in soil by the slowly-descending heat of the previous day, which forces interstriaal water into channels of easiest flow.

Another explanation rests on the fact that during the day evaporation and vegetable transpiration are at a maximum, whereby the flow of sub-surface water is diminished.

At night, with the cessation of these activities, the flow is relatively increased, and valleys receive their greatest load, with the result that their sides close inwards. To support the idea that water load plays an important part in the fluctuation of level we have the repeated observations that during wet weather, when we see water accumulating in the beds of valleys, the heeling over of the booms of horizontal pendulums is towards the loaded district.

The main point, however, to which I desire to draw attention is not so much the explanation of curious phenomena, but simply to the fact that Horizontal Pendulums may, under certain conditions, be influenced by hidden water loads. The investigations that this suggests should be of particular interest in certain parts of South Africa. For example, do the fluctuations of the subterranean water tapped in the Karoo affect the surface level? If they do, then the revelations of a pendulum may play an important part in the opening up and the settlement of a district.

Whether this type of seismograph will be used as an assistance in the prediction of weather is a matter worthy of some consideration. The Barometer gives the atmospheric pressure where it is installed. The Horizontal Pendulum, under certain conditions, swings to the