DEEP BORINGS, &C. 
49 
Specular Iron Ore, No. 44 ; Agate, No. 5. 
On a pedestal close to the model of the Auvergne volcanoes is 
a magnificent specimen of specular iron-ore on lava, from the 
Island of Ascension. The formation of specular iron-ore in 
volcanoes probably results from the action of watery vapour on 
perchioride of iron ; hydrochloric acid being set free, whilst 
peroxide of iron is deposited in a crystalline form. 
On the opposite side of the museum, close to the model of 
London, is an exceptionally fine polished specimen of South 
American Agate, on the pedestal No. 5. Nearly all the agates 
which are brought into commerce are obtained from Uruguay, in 
South America, whence they are exported to Germany, and are 
cut and polished in the neighbourhood of Obersteiu, on the River 
Nahe, a tributary to the Rhine. (See p. 54.) 
Cores from Deep Borings. Case No. 41. 
A very interesting series of specimens showing the strata 
passed through in various deep borings, chiefly in the neighbour- 
hood of London, is arranged in this case. 
In the years 1855, a boring for water, known as the Kentish 
Town boring, undertaken by the Hampstead Water Works 
Company, at a spot situated at the foot of Highgate Hill, passed 
through the Chalk, the Upper Greensand and the Gault, and 
then, at a depth of about 1,114 feet, entered red rocks of 
doubtful age, specimens of which are here exhibited. Soon 
afterwards a boring at Harwich showed that the Gault was 
there immediately followed by a dark slaty rock, apparently of 
Lower Carboniferous age. A suite of specimens from the 
Harwich boring is in this case. 
From these two borings it was discovered, for the first time, 
that in certain parts of the East of England, the strata below 
the Gault did not follow in their normal sequence, and that 
rocks of Palaeozoic age might, by the absence of many members 
of the Secondary series, be brought up within a moderate 
distance of the surface. No further evidence respecting these 
underground old rocks was, however, obtained until the year 
1877, when a boring at Meux’s Brewery in Tottenham Court 
Road, showed that Upper* Devonian rocks, fossiliferous and 
highly inclined, were present at a depth of only about 1,066 feet. 
In addition to the specimens in this case, others will be found 
mounted on the pedestal No. 16. Shortly afterwards the New 
River Company struck fossiliferous Devonian shales at 980 feet 
in a boring at Turnford, near Cheshunt ; whilst at Ware, in Herts, 
Wenlock beds (Upper Silurian) with characteristic fossils, were 
obtained from a depth of less than 800 feet. Some remarkably 
fine cores from these two borings are exhibited at the foot of the 
Staircase, on each side leading to the Gallery. 
Within the last few years deep borings have multiplied, and 
samples of cores from many localities are collected in this Case 
