162 
NATURE 
[ FEBRUARY 3, 1923 

The Lourenco Marques Meeting of the South African Association. 
"THE twentieth annual meeting of the South 
African Association for the Advancement of 
Science was held at Lourengo Marques, in the Lyceu, 
on July 10-15, under the presidency of Dr. A. W. 
Rogers. The meeting was well attended and was 
very successful. About fifty papers were read. An 
official welcome was given by the High Commissioner 
for Mocambique and the Mayor of Lourengo Marques. 
There were various visits and excursions to places 
of local interest, both on the Bay and inland, and an 
official banquet was given to members at the new 
Polana Hotel. 
A popular lecture, illustrated by lantern slides, 
was given by Mr. C. Graham Botha, Keeper of the 
Archives at Cape Town, on “ The Early Development 
of South Africa.” 
The South Africa medal and grant were awarded 
to Dr. I. B. Pole Evans for his contributions to 
botanical science in South Africa. 
The presidential address by Dr. Rogers dealt with 
“ Post-Cretaceous Climates of South Africa.” Four 
types of evidence on which recognition of former 
climates depend were discussed. These were the 
character of the rocks during the period concerned, 
the shapes of the land surface resulting from long 
duration of more or less constant climatic conditions, 
the distribution of animals and plants, and the 
historical records of man; the lithological evidence 
is the most important for all but relatively recent 
times. Each of these factors. was considered in 
detail as regards South Africa, the evidence being 
considered from post-Cretaceous times only. His- 
torical records of the past climate in South Africa 
apply closely to present-day conditions, allowance 
being made for the progressive settlement of the 
country. From personal survey work Dr. Rogers 
concluded that in certain districts no deterioration 
of climate or marked loss of water has taken place 
during the last fifty years. The various lines of 
evidence point to the conclusion that during post- 
Cretaceous times the climate of South Africa has 
fluctuated within rather narrow limits; that there 
has not been a Pluvial period, if by that term is 
implied a long period of much greater rainfall over 
the whole country; that a general lowering of 
temperature in the Pleistocene may have given the 
Kkarroo and Southern Kalahari rivers longer periods 
of flow, but that this more humid era in those regions 
had come to an end long before human evidence 
can be drawn upon for an account of it; and that 
South Africa, like North Africa, the Americas and 
Australia, bears evidence to a shifting of the climatic 
belts in the Pleistocene and subsequent times. 
The presidential address to Section A on “‘ The 
Réle of Astronomy in the Development of Science,”’ 
was given by Dr. M. A. Peres, Director of the Campos 
Rodrigues Observatory, Lourenco Marques. He 
summarised ably some of the chief discoveries and 
laws in astronomical science, and showed their 
influence on subsequent research in other branches 
of physical science. Thus, astronomical observa- 
tions led to the formulation of the laws of Newton, 
which opened a vast field of other researches. Similar 
astronomical observations leading to the work on 
the velocity of light were the first step towards 
wireless telegraphy. The indebtedness of optics 
especially, to astronomical research, was also in- 
dicated, and it was pointed out that the chief con- 
firmation of Einstein’s theory was dependent on 
astronomical observations. 
‘The Influence of Mineral Deposits in the Develop- 
ment of a Young Country ”’ was chosen by Dr. E. T. 
NO. 2779, VOL. 111] 
Mellor as the subject of his presidential address to 
Section B. This was first illustrated by reference to 
the Tsumeb Mine in South-West Africa and Broken 
Hill in Rhodesia. The Tsumeb*Mine brought about 
the building of a railway from the coast to the mine, 
350 miles away. The Broken Hill Mine practically 
determined the course of the main line of the Cape 
to Cairo railway. The railway system of the Union 
of South Africa has been influenced by the goldfields 
of the Witwatersrand. The tracing of the extension 
of these gold reefs eastwards, the location and 
exploration of new coalfields, and systematic boring 
for possible oilfields, all depended on an adequate 
geological survey. The extension of the Witbank 
coalfield, though proved and ready for easy exploita- 
tion, is suspended because of lack of transport and 
a market. The connexion of mining developments 
with research in other sciences was considered, and 
it was shown that in the gold industry South Africa 
possesses a field sufficiently extensive and stable to 
exert more than a temporary influence on the country 
generally. ; : 
The presidential address to Section C was given 
by Prof. D. Thoday, and dealt with “‘ Carbon 
Assimilation’ in plants. The great advances in 
the knowledge of the subject due to the work of 
Blackman in Cambridge and Willstatter in Berlin 
were summarised, attention being directed to the 
work done on pigments. The réle of iron and of 
magnesium were also discussed. The application of 
the subject with special reference to South African 
conditions was detailed. The plants of the open 
veld are exposed to the full blaze of the sun through 
most of the year, and this is more than sufficient 
to enable an ordinary green leaf to assimilate all 
the carbon dioxide that it needs. Paler green or 
golden leaves demand more intense light than dark 
ones for their full activity. Consequently, veld 
plants have paler leaves, and in extreme cases the 
leaves are almost greenish yellow. Particulars of 
internal structure affecting depth of colour were 
also discussed, as were leaf forms and patternings, 
and it was emphasised that such features are not 
merely adaptations to a dry climate but that their 
effects on photosynthesis of carbon dioxide are 
probably of equal significance. 
The presidential address to Section D was delivered 
by Dr. Annie Porter, her subject being “ Some 
Modern Developments in Animal Parasitology.” 
After a general introduction dealing with degrees 
of parasitism, specificity and the like, recent advances 
in protozoology were first considered. Attention 
was directed to the conflicting opinions as to the 
existence of races of Entameba_ histolytica. The 
work of Taute and Huber on the non-identity of 
Trypanosoma rhodesiense and T. brucei, as shown by 
direct inoculation of the human subject with game 
trypanosomes, was discussed, and attention was 
directed to work on induced herpetomoniasis in 
vertebrates. Flagelloses of plants were described, 
especially those due to herpetomonads, some of 
which had been proved capable of infecting mammals ; 
also the spirochetes, amoebe, and other parasitic 
Protozoa found in plants and their reactions on their 
hosts were noted. Recent work on neuromotor 
apparatus in Protozoa, and on various organisms — 
viruses associated with infective 
(spirochetal) jaundice, trench fever, and typhus 
were discussed. In helminthology the interesting 
life-histories of schistosomes in various snails, of 
and filterable 
Clonorchis in snail, fish and man, of Paragonimus — 
in snail, crab or crayfish and man, and recent work — 

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