I always like climbing up above Derwent Water because you can look down on the wave patterns. Yesterday we were looking down from Walla Crag when the passenger boat came past. If you enlarge the photograph you can see the characteristic wave pattern behind the boat. It is called a Kelvin Wake after Lord Kelvin the Scottish physicist who first did the analysis. I haven't had time to read the mathematics in detail - I'll need to get back to you - but it seems that the angle may be just over 19 degrees whatever speed in deep water. I need to check this claim. I got my information from http://www.wikiwaves.org/Ship_Kelvin_Wake
When we were on the summit another bloke pointed out the marking in the rocks shown below. He said he thought it was a benchmark, which was a topic on this blog in September. I have checked the benchmark listing website and it's not recorded, so the jury is out. It doesn't look natural but it is flat, not vertical. It has no top line.
