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What has been done in other countries can be done here, but it will require the combined energy of the people to accomplish it.

I would urge you to bear in mind that the prosperity of South Africa does not depend alone on its mineral wealth; while these enormous productions are being taken out of the earth, we, as an Association, must not be unmindful of our duty to the country at large.

As Cobden remarked on the future greatness of Manchester, "just in proportion as mental development goes forward, and in proportion to the development of wealth and mental resources, just in the same proportion will our destiny be exalted, or the very reverse."

While you are devoting your time to scientific research, to technical work in connection with the great mining enterprises, and to various other pursuits, do not neglect the intellectual training of the young men and women of the country, for upon them the future prosperity of South Africa will depend."

The struggle for existence has become so acute that the man who does not use his brains to assist him in his work is left far behind those who have had proper education and training. It is the duty of an Association like this, the influence of which is far-reaching, to do all in its power to improve the educational facilities, so that the youth of these colonies may be given opportunities for higher mental training.

Before closing my address, I beg leave again to express my regret that I am prevented from being with you on this occasion, and to thank the members of the Council for the honour they have conferred upon me.

SECTION A.

Astronomy, Chemistry and Metallurgy, Mathematics,

Meteorology, Physics.

Section A.

PRESIDENT'S ADDRESS.

2. THE DIURNAL VARIATION OF BAROMETRIC

PRESSURE.

By J. R. SUTTON, M.A., F.R.Met. S.

me.

The present occasion is unique in my experience, inasmuch as it is the first scientific meeting I have ever personally addressed. I have contributed occasional papers to scientific societies, it is true, but in every case I have had to depend upon some friend to read them for You will see from this that the South African Association for the Advancement of Science is scarcely to be congratulated upon its President of Section A. If a moral may be drawn from the situation, it is that it is a mistake to expect every town which entertains the Association to provide Presidents and Sectional Officers. You would have got a President with more experience, and altogether better suited to the position, by selecting officers on their merits, and not on account of where they live. Any little inconvenience incurred by appointing officers not in residence would be more than counterbalanced by their suitability.

Another reason for quarrelling with my position here is that I am not qualified to pass in review, according to orthodox tradition, the present state of the sciences comprised in this section. My topic has necessarily to be special, confined to one branch of study; if I were to attempt more I should be speaking of things concerning which some of my hearers would know more than I do.

With this preface I have to ask for some forbearance and attention while I bring before you some aspects of the fundamental problem in Meteorology (one might almost say the fundamental problem in Geo-Physics): the semidiurnal oscillation of the barometer. The case is this: All over the world, on land and sea, in valleys and on mountains, the barometer rises and falls twice a day, the maxima of pressure coming in general before Noon and before midnight, the minima a few hours before sunrise and before sunset respectively. It will be convenient to denote these in the following way:

m1, the early morning minimum ;
M1, the morning maximum ;
m2, the afternoon minimum; and
Ma, the evening maximum.

1

Some typical specimens of the diurnal variation of the barometer shewing these phases are given in Figs. 1. and 2. We see from these

TYPICAL BAROMETER CURVES

N

ANANITO
4=6672cm

GREENWICH
4=51°24′ M.

-KIMBERLEY
4=28°43′5

DARESSALAM

9=62 lag′5.

| Fig. 1.

SCALE OF PRESSURE VARIATION: 100 Divisions = 11494

that the mean annual range of the diurnal variation of the barometer decreases from the equator to the poles with some differences in the

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