To locate this EarthCache, you need to get down to the side of Eller Beck from Mill Bridge. There is a path down to the location. If the beck is running high or fast, then please do not attempt the cache. You need to be in the area where the beck goes under the bridge, there is NO need to go any further into the darkness. You should not need a torch to do this cache. You may however get wet feet.
The cache can only be done by accessing it from below the bridge, and it is not the bridge which crosses the nearby canal.
I want you to look at the curved walls of the bridge. Now the bridge is made out of sandstone blocks, with mortar inbetween. It is the mortar that we are interested in, or rather what has occured as a result of it.
Mortar is traditionally a mix of lime and sand. Lime consists of calcium oxide, gained from heating limestone. At first there would have been neat lines of mortar between the sandstone blocks, but has time has gone on, and the structure has been exposed to water, the calcium oxide reacts with water to form calcium hydroxide. Over time, rainwater carries calcium hydroxide in a solution, which when it comes into contact with air, it reacts with carbon dioxide and calcium carbonate is preciptated. What you can see on the walls of the bridge is calcium carbonate.
In a cave the precipitation of calcium carbonate forms both staligtites and staligmites. Though in a location outwith of a cave, these deposits are known as calthemites. A calthemite is a deposit derived from concrete, lime or mortar, and they grow under man made structures, and look like cave structures.
Calthemites can appear in many forms, which are :
Flowstones, which looks like a flowing river off calcium carbonate, this tends to be rippled.
Straw Staligtites, which are long thin straw like structures.
Calthemite staligmites, which are a build up of calcium carbonate on the floor, which gradually gain height.
Calthemite rimstones, these form on the floor as a gradually sloping structure.
When a staligtite and staligmite join, it is known as a column.
This being an earthcache, in order to log it, I ask that you answer some questions. Please send them to me, and do not include them in your log. You can send them to me by using the message facility or email, both of which can be found by looking at my profile.
1. Please tell me what forms of calthemites you can see.
2. What colour are the calthemites, why is this?
3. If you can see a stalactite, please tell how long is the longest one that you can see?
4. So as to prove that you have been under here, please tell me which other colours you can see on the walls of the bridge, and is theer evidence of one or two bridges?