Finding out about Plum Concrete

 

The notice board by the Elan Valley dams mentioned "concrete with plums". I'd not heard of that before. Turns out it is plain concrete with large rocks placed in it. When water is added to cement, an exothermic reaction takes place that releases a lot of thermal energy. The amount released in something the size of a dam would be huge. If maybe 40% of the mix is rocks, then this reduces the amount of thermal energy released.

Haltwhistle Viaduct like a parabolic reflector for sound

 Where Haltwhistle Viaduct crosses the Tyne there is a weir.

Approaching from the other side there was a roaring coming from above me that sounded like a strong wind. The sound of the water was being reflected and focused by the curved underside of the arch.

Avoirdupois again

This was in the museum at Llandrindod Wells. I've never seen the avoirdupois system made so prominent, perhaps to distinguish from other uses of LB. Interested to note that they made an international standardised version as late as 1959 so a pound is a pound in all countries.

Fence post machine

This machine is a wonder. It holds the posts in place and then hammers them in. The hammering action involves hoisting a metal cylinder and letting it fall. I am estimating the cylinder to be 50cm high with a diameter of 20cm. That gives a volume of about 15000 cm^2. If it is steel, the mass is 125 kg. If raised to 50cm above the post, it will hit it with a theoretical velocity from the v^2=u^2 + 2as equation, giving about 3m/s. Suppose it stops in 0.1 second on hitting the post. Force = change in momentum/time taken = 125 x 3 / 0.1 = 4kN to 1 sf. 
 

Lerwick Power Station

I always like researching the power supplies for islands. I spotted this at the far end of Stornoway harbour. You can read about it here. It is on the wonderfully named Battery Point - in the old usage of a gun battery! It seems that the power station is now used as a top up supply in the winter when the demand is higher than can be supplied from the mainland. I'm interested that there are plans for an HVDC cable to connect up the wind turbines to the mainland as well.

 

Metamorphic aureole at the other Wasdale

 

This picture shows a rock formation with the ruined Wasdale Farm near Shap. The hill behind is the site of the Shap Red Quarry, so is the location of the Shap Granite intrusion. Just a few hundred metres away, the rock is very different. The picture below shows layers, so I had come out into the metamorphic aureole where the heat had baked the existing country rock.

Polarisation reverses the colours

 

My polarising sunshades produced a diffraction effect on the edge of this cup of water. Pinker colours at the bottom with yellow and green above. When I rotated the polariser through 90 degrees, the order of the colours reversed.

Strange sundog

 

This was a strange optical phenomenon. Very high thin cloud produced a sundog - the small rainbow effect that appears either side of the Sun. However a lower layer of cloud was obscuring the Sun so there was no apparent cause for the tiny rainbow!