The fountain is constructed in a gothic style with elaborate canopies and scrollwork. Predominantly sandstone, it blends with the viaduct and the adjacent more recent walls constructed since the fountain was rotated c90 degrees in the 1970s.
There are two key rocks used in the fountain's construction:
Sandstone A sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed of quartz or feldspar. Like sand, sandstone may be any colour, but the most common are tan, brown, yellow, red, grey, pink, white, and black. The formation of sandstone involves two principal stages. First, a layer or layers of sand accumulates either from water (as in a stream, lake, or sea) or from air (as in a desert). Typically, sedimentation occurs by the sand settling out from suspension. Finally, once it has accumulated, the sand becomes sandstone when it is compacted by the pressure of overlying deposits and cemented by the precipitation of minerals within the pore spaces between sand grains.
Some sandstones are resistant to weathering and erosion, yet are easy to work. This makes sandstone a common building material. However, some that have been used in the past have been found less resistant, necessitating repair and replacement in older buildings. It is this weakness that leaves the date of this fountain uncertain as the piece bearing the crucial final digit of the date is too badly eroded to decipher.
Granite A common type of igneous rock . Granite is formed when magma (molten rock) is forced between other rocks in the Earth's crust. As it cools slowly large crystals are formed giving it a coarse texture. Granite is made up of a number of minerals, but predominantly consists of quartz, feldspar and mica. Quartz crystals often resemble smoky glass when polished. Feldspar often provides the colour in the granite and is softer than Quartz so tends to erode faster. Granites can be predominantly white, pink, or grey in colour, depending on their mineralogy.
The word "granite" comes from the Latin granum, a grain, in reference to the coarse-grained structure. Granite is hard and tough, and therefore it has gained widespread use throughout human history as a construction stone. Granite is a hard stone and requires skill to carve by hand. Until the early 18th century granite could only be carved by hand tools with generally poor results. However, the invention of steam power allowed for more effective carving of the stone. The fountain contains two very distinctly coloured examples of the rock.
Weathering and erosion of stones. There are two effects at work on the stones within the fountain. Weathering, occurs on the stones without movement of the stone particles, while erosion involves some movement of particles and surface materials. Weathering and erosion take place in the same locations, affecting the same stones, but erosion involves the movement of loosened particles and surface materials downwards via the force of gravity. Particles, such as small pieces of rock, sand and dirt dislodge during erosion, often triggered by wind or rain. There are three potential effects at work on the both the sandstone and granite in the fountain which give the monument its current appearance.....
Mechanical Weathering. Mechanical weathering occurs when temperatures fluctuate causing the rock to expand and contract, or where water inside of the rock freezes and expands causing cracks which eventually break the rock apart.
Chemical Weathering. Chemical weathering occurs when the surface of the rock reacts with the environment and the chemical reactions between the two cause the rocks to soften and make them more vulnerable to erosion.
Biological Weathering. Biological weathering occurs when plants like lichens and mosses come into contact with, or grow on the rock and gradually either break down the minerals in the rock and eat away at the rock surface, or where root structures cause the rock to crack.
To log the cache you can send your answers through Message Centre or via Email to the following questions. Do not post the answers in your log !
Q1. The three stones are close together at the base of the right hand pink granite pillar. Touch the three principle rocks in the construction at this point - Sandstone (pedastal below pillar), Grey Granite (fountain backboard) and Pink Granite (pillar). Rank them from roughest to smoothest.
Q2. Examine the inscription on the canopy which is now unclear through weathering. There are three types of weathering - chemical, mechanical and biological. Which do you think has caused the erosion in the sandstone ?
Q3. Why do you think that the Grey Granite has been used around the fountain head ?
Q4. Examine the pink granite closely and describe the rock. What noticeable features does it have and how big are the particles?
Q5. What's in the lower small arch at ground level ? Bend down and have a look ! Describe it and the rock it is made from.
Optional extra. Take a picture of yourself with the viaduct or fountain, but please not of what's in the lower arch, and post it in your log.
If you have any other old pictures of the viaduct or fountain then please post them too !