1896-1904 at East London, and compared them with the simultaneous temperatures at Durban and Kimberley. The following are mean annual results for penthemera, of which the night of a cold wind is the central night, together with the normal means. TABLE 6. Mean Annual Minimum Temperature of Cold Spells at East London, compared with the simultaneous Temperatures at Durban and Kimberley. An examination of these numbers shews that the cold weather is general throughout the country, but that the true epoch of minimum is earliest on the central table-land, and latest at Durban. In fact, the lowest point of the curve of departure from the mean temperature of the five days comes between the second and third day at Kimberley, slightly later than the third day at East London, and between the third and fourth days at Durban. This is a remarkable result, considering that the barometric conditions upon which these low temperatures depend travel from SW. to NE., and are therefore felt earlier at East London than at Kimberley by many hours. If the dependence of the temperatures upon the pressures were absolute we should expect the temperature wave, like the pressure wave, to be felt first at East London, and almost simultaneously, later on, at Durban and Kimberley. It seems to follow, then, that the cold winds in question, like the hot winds, must originate on the tableland, and move downwards to the coast. An analysis of the barometric pressures, which it is unnecessary to give here, supports this view, anti-cyclonic conditions being the rule. For the purpose of investigating the wind movement I have only had access to the anemometer records of East London for the three years 1898-1900; but of the 31 instances of low minimum temperature at East London in those three years 29 occurred with winds blowing off the land, and the other two with wind blowing parallel to the coast, one in December strong from the SW., and the other in October strong from a north-easterly direction. I am inclined to think that in both these exceptional instances there must have been a strong admixture of land wind entering from above. The average velocity of the wind at the time of minimum on the third day in the 31 instances between midnight and 8 a.m. was 19 miles per hour, i.e., about a mile an hour faster than the normal. It is evident from these facts that the cold winds of East London are true bora winds, similar in every respect to those of Dalmatia. A similar investigation for the occasional low minimum temperature periods at Durban gives 83 typical instances, not, as it happens, generally falling on the same day as those in the above comparison for East London. In most of these there is either calm or light wind, and in that respect they differ from the East London cases. The annual averages are: TABLE 7.-Mean Annual Minimum Temperature of the Cold Spells at Durban, compared with the simultaneous Temperatures at East London and Kimberley. Here we see that while the epochs come in the same order as in Table 6, as might have been expected, the low temperature waves of Durban are not so pronounced at East London and Kimberley as the low temperature waves of East London are at Durban and Kimberley. And an examination of the individual instances shews the reason to be that many of the exceptionally low temperatures felt at Durban are not accompanied by any great fall of temperature inland, but, surprisingly enough, are associated in some way with winds from the sea. Nineteen of the 81 cases of low temperature averaged in Table 7 were associated with winds having a component off the sea, that is to say, blowing from anywhere between S. round by E. to ENE. The following are averages for the three stations for the nineteen occasions upon which the wind at 9 a.m. at Durban came in from the sea * TABLE 8.-Average Minimum Temperatures of the Cold Spells at Durban, with Sea Winds. *In eighteen out of the nineteen instances the wind was also blowing off the sea at 3 p.m. on the previous day: The shape of the Durban curve is here nearly the same as in Table 7, where all the cold spells are included, but the epoch is somewhat earlier. Also the average is rather greater, but that is accounted for by the circumstance that cold winds from the sea are not met with during the winter months. The East London and Kimberley comparative values are elevated somewhat for the same reason. While these peculiar conditions are in progress, pressure on the table-land is moderately high, the averages at 8 a.m. at Kenilworth being : ... 26 108 inches. Fourth Day 26.129 inches. 26.116 First Day Second Day Third Day and the wind on the table-land shifting from easterly components to westerly. Thus the low temperatures at Durban coincide with the following sides of moderate barometric crests* and the incidence of westerly winds; also the rise of temperature at Kimberley on the fourth and fifth days of the penthemera corresponds to the falling pressure. The average temperature on the table-land for the five days is probably somewhat greater than the mean minimum temperature of the months in which they mostly occur. Now, there is one very remarkable characteristic of these cold sea winds, and that is their dryness. Not one of them carries the quantity of moisture proper to the time of year, the average for them all being fully 15 per cent. short of the mean, and, in spite of their low temperature, they appear to be far from humid. One would scarcely expect a cold, dry wind to blow over an ocean whose water is for its latitude among the warmest in the world. Therefore, because of its dryness, it is probably a re-entering land wind which has somewhere moved outwards, but returned after describing a very short path over the ocean. But how, then, is its temperature to be accounted for? If it originate on the central table-land it must have started as a warm wind, and by dynamic heating in its descent should become still warmer, and thus reach the coast as a warm wind. The cause of its low temperature is therefore still uncertain. In this connection it would be interesting to know whether snow is lying on the crests of the Drakensberg while these cold sea winds are blowing. If not, then the only likely place of their origin seems to be in the main westerly atmospheric drift above, from which they slant downwards and inwards in response to the falling pressure. * The_barometric changes at Durban are appreciably the same as those at Kimberley at these times. DURBAN, NATAL. BY R. FERMOR RENDELL, B.A., F.R.A.S., OF THE OBSERVATORY, DURBAN, NATAL. The Paper contains: [ABSTRACT.] (a) Remarks on the subject, drawing attention to its (c) A comparison is shown to prove the superiority of the (1) The predicted times of High Water given in the (2) The predicted times calculated by my new method. (3) The observed times supplied by the Engineer of the Natal Harbour Works. (4) The discrepancies between the predictions in the Natal Directory and the observations. (5) The discrepancies between my predictions and the observations. The results show that the new method is vastly superior to the old. About half of the observed times differ by more than threequarters of an hour from the old predictions (which are sometimes too early and sometimes too late), while the majority of the new predictions are within a quarter of an hour of the observed times. For the period of nine months, commencing September 1st, 1905, the average discrepancies are 46 minutes and 14 minutes respectively. During this period 495 observed times were investigated. The following summary indicates the nature of the results : By investigating a longer series of records, the writer hopes to be able to deduce still more accurate values for the quantities in his tables. TRANSVAAL. BY HERBERT INGLE, B.SC., F.C.S., F.I.C. Though at present the economic importance of the Transvaal depends mainly upon its mineral resources, there can be no doubt of the vital interest attached to the agricultural possibilities of the country if it is to become the permanent home of the colonist. A factor of the utmost importance in determining these possibilities is the character and composition of the soil, for though climate, rainfall, water supply, possibility of finding a market for produce, and other circumstances, to a great extent determine the progress of agriculture as a business, these become merely insignificant considerations if the soil be not productive. The chemical composition of the soil, though by no means the only item of importance in assessing its productiveness, is certainly a great factor in gauging its potential fertility. Unless the constituents of plant food are present in the soil in sufficient quantity, no combination of favourable circumstances as to temperature, water supply, and other features, will yield good crops. Until recently, but few analyses of Transvaal soils had been made. The few that were available indicated that, compared with European soils, those of the Transvaal were poor in most of the important constituents of plant food, and that, judged by the experience of ordinary temperate climates, they were in urgent need of manures. During the past three years, analyses of about 160 samples of soil from various parts of the Colony have been made in the Chemical Laboratories of the Transvaal Department of Agriculture, so that we are now in a position to speak with some degree of confidence as to the general character of our Transvaal soils, so far, at least, as their chemical composition is concerned. In a tract of country so extensive as the Transvaal, we find, as is to be expected, considerable differences in composition among the samples, but, though here and there are to be found patches of soil rich in most manurial ingredients, the greater number of samples. indicate that the soil, in general, is poor in organic nitrogenous matter, phosphates, and lime. Potash compounds, with some few exceptions, are generally sufficiently abundant. Again, speaking from the experience of European countries, most of our Transvaal soils would appear to need additions of combined nitrogen, phosphates and lime, in order to possess average fertility. But to judge soils in tropical countries from the standpoint of the experience obtained in temperate and less sunny climates is not fair. It is found in actual practice that a soil of extreme poverty, compared with average English soil, will often, in this country, yield quite respectable crops. This is the experience in other parts of the world, e.g., Assam, where the tea soils of great apparent poverty, nevertheless yield good Several factors, no doubt, are influential in bringing this crops. |