Bridging the Tay - Sandstone style. EarthCache
Hidden : 1/13/2015
Difficulty:
1 out of 5
Terrain:
1 out of 5

Size: Size: other (other)

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Geocache Description:

There has been a bridge over the river Tay into Perth since the 12th Century, sited at the lowest crossing spot. The last four on this site were destroyed or damaged by floods. Completed in 1771 a halfpenny toll was charged to cross the bridge.ย  The total construction cost came to ยฃ26,446. This is an earthcache, i.e. no physical box to find, you are here to observe the construction materials used, read the information provided and then answer a few easy questions.

Please note this is a fast flowing tidal river, so please watch youngsters and four legged friends.

PLEASE DO NOT ATTEMPT THIS EARTHCACHE SHOULD THE FLOODGATES BE CLOSED

The coordinates take you to an information board below the western end of Smeaton's bridge beside its dry arch. The bridge is named after John Smeaton, architect and engineer.

SANDSTONE
Sandstone is a sedimentary rock, composed from sand and rock grains, mainly of quartz and possibly feldspar origin, some of the most common minerals in the Earth. It varies in appearance, with colours from a pale buff to a yellow, pink right through to a dark red and even lightest grey. It could contain layers and imperfections of other minerals within its makeup. It is porous and has varied grades of hardness, making it ideal to cut and carve for construction or hard enough for pavements and millstones.

Like other sedimentary rocks, its formation is made up of layers of sand as it accumulates in rivers and lakes, or air blown like in a deserts. These grains eventually settle and become compacted by pressure and heat due to the weight of overlying deposits, together with minerals soaking into the porous grains.

The percentage of different minerals and 'foreign' objects (stones, shells, plantlife,) determines its colour and overall appearance as well as being a great source of fossils.

WHINSTONE
Whinstone Is a dense smooth hard rock, usually a black or a very dark rock, sometimes with a green or red hue, a generic name used by the quarrying industry consisting usually of igneous rocks basalt and dolerite. Here in central Scotland it is classified as a quartz dolerite.


On the north side of this archway you will find the various flood heights on the bridge wall, showing you just how much water can flow through the city of Perth, please be aware there is an open slipway here to the water. On the south side in front of the railings is an information board. You can observe just how shallow the river is at this crossing point with its rocky riverbed.

Using the information supplied and applying your observation skills please answer the following questions:

1. Your first observations are made from the noticeboard south side of the dry arch.
a) Smeaton's bridge named after John Smeaton, architect, by what other names is this bridge known?
b) How many bridges are mentioned on the noticeboard?
c) Perth castle got swept away in a flood 1209. Where did it used to stand?

2. View the complete bridge as it spans the river, observe its construction noting what materials have been used to build this impressive bridge. Would you conclude it to be mainly whinstone or mainly sandstone?

Now walk through the dry arch and turn to look at the bridge from its north side.
3. a) What is the most recent flood date added?
b) Looking at this date observe the texture of the stone blocks surrounding it. What imperfections can you see?

4. Looking at both building materials, list the obvious differences between the two that you can see here. (sandstone/whinstone).


5. Now simply message or email us your answers not forgetting to include your reply address BEFORE logging your experience online. Please feel free to add any photographs to your online log.

Thank you for visiting this earthcache.

Additional Hints (Decrypt)

Lbh fubhyq or fgbbq ng evire yriry orybj gur oevqtr. Cyrnfr zrffntr lbhe nafjref naq gura ybt bayvar. Gunax lbh sbe ivfvgvat guvf rnegupnpur.

Decryption Key

A|B|C|D|E|F|G|H|I|J|K|L|M
-------------------------
N|O|P|Q|R|S|T|U|V|W|X|Y|Z

(letter above equals below, and vice versa)


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