756 Meeting of the British Association. | Oct., 
of level), a great alteration has taken place in comparatively recent 
times. Mr. Bates concludes that the mouth of the Amazons was not 
formerly a wide gulf, filled up since by fluvial deposit, but that it was 
bridged over by a chain of islands, separated by narrower channels 
than at present. This is illustrated by the fauna and flora. 
An interesting memoir was communicated by Mr. James Fox Wilson, 
on the desiccation of the interior of Southern Africa, by the gradual 
drying up of large tracts of country in the Bechuana country. In this 
district the natives are cutting down all the trees, and burning the 
dried trailing plants, allowing the fires to extend to the mountains. 
In other parts, the settlers burn the herbage in winter, to have fresh 
pasture in spring. The effect of this laying bare the surface, is to in- 
crease the drought, and the country will become seriously injured by 
consequent change of climate. It was generally agreed in a dis- 
cussion which followed the reading of the paper, that in all civilized 
countries the supply of rain has long been diminishing, and that this 
is mainly due to agricultural operations. 
Dr. Livingstone’s and other communications must be deferred ; we 
cannot do them justice here. 
Mecuanroau Science. (Section G.) 
Sorby on Photographing the Structure of Metals.— Selwyn and 
Fairbairn on Submarine Telegraphy. 
Mr. Sorsy exhibited photographs taken by Mr. Hoole, of Sheffield, 
under his superintendence, illustrating the condition of iron and steel. 
The photographs were taken direct from the microscope. The 
objects are largely magnified, and the results extremely satisfactory. 
The metal was prepared by Mr. Sorby by acting on a polished surface 
with weak acid in a way already known, but the result now obtained 
is quite new and highly instructive. Among other conditions of iron 
we have: (1) Meteoric Iron, exhibiting its crystalline nature in the 
most perfect manner. (2) Grey Pig. Here crystals of graphitic carbon 
are seen shooting through the mottled surface of the metal. (38) Re- 
fined Cast-iron. Long lines of hard parts of the metal (probably 
spiegel-cisen) have arranged themselves in layers. (4) Slightly- 
hammered Bloom. The imperfect and confused state of the iron and 
slag irregularly mixed are strikingly shown. (5) Bowling Bar-iron. 
Tn this, the slag being driven off, and the metal rendered more compact, 
the texture is seen. The result is very curious and valuable, and con- 
trasts singularly with (6) Swedish Iron—a steel-like substance, quite as 
different in texture as in its properties. (7) Armour-plate is a curious 
variety of No.5. (8) Blister-steel. The effect of the converting 
furnace is very singular and unexpected, and is well seen in this 
photograph ; while (9) Cast-steel shows the total change produced by 
an even mottled state of the metal, and the general uniformity of the 
sections of crystals cut transversely. 
