MODEL OF LONDON. 
47 
Another prominent object in this case is a gold snuff-box, set 
with a large number of diamonds, and ornamented with ail 
enamel portrait of the Emperor of Russia, Alexander II. This 
box was presented to Sir R. I. Murchison by the Emperor 
N icholas. 
Geological Model of London. No. 3. 
This large Model was constructed by the late Mr. T. B. 
Jordan, under the superintendence of Mr. W. Whitaker, of the 
Geological Survey. It represents a tract of country around the 
metropolis as a centre, measuring about 15 miles from east to 
west, and about 11 miles from north to south ; or a total area of 
something like 165 square miles. The horizontal scale is the 
same as that of the county maps of the Ordnance Survey, 
namely, six inches to the mile ; whilst the vertical scale is 200 
feet to the inch, or about 4*4 times as great as the former. Had 
the vertical scale been the same as the horizontal, as was 
originally intended, the heights on tae model would have been 
so insignificant, that the highest point which it includes, the top 
of Hampstead Heath, would have been represented by a rise of 
little more than half an inch. An exaggerated vertical scale 
was therefore absolutely necessary in order to exhibit with due 
effect the undulations of the ground. It will be observed that 
although the area around the metropolis is popularly known as 
the “ London Basin/’ this basin is in fact nothing more than an 
extremely shallow depression ; and even with the exaggerated 
dip represented in the model, the beds slope towards the centre 
of the trough at a very slight inclination. 
The oldest rock which comes to the surface within the area of 
the model is the chalk : but several deep wells sank in the 
London basin have reached the underlying rocks. The beds 
below the chalk are seen in section on the sides of the model. In 
fact the model is constructed in nine separate blocks, five of 
which can be raised by means of a winch so as to expose the 
sections on their inner sides. # 
By far the greater part of the country represented in this 
model is formed of strata overlying the chalk and belonging to 
the tertiary series. These consist of the Thanet beds, imme- 
diately above the chalk ; followed by the Woolwich and -Reading 
series, the Oldhaven beds, and the London Clay. This clay, which 
may reach a thickness of about 400 feet under the Metropolises 
covered on the hills of Hampstead and Highgate by sandy beds 
known as the Lower Bagshot Sands. The post-tertiary gravels, 
sands, clays, brickeartb, &c., spread more or less extensively 
over the older strata, are grouped together under the general. 
* Visitors desirous of inspecting the sections on the sides of the movable blocks, 
should apply to the officers of the Museum for permission to raise them, but should 
not otherwise attempt to disturb the model. The geological maps under the gallery 
should be drawn up and down by the policeman on duty, and not by the visitor. 
