The special light in St Ives is not a media illusion (Letters, 15 December). The town is situated on a promontory with wide beaches on three sides. They are made of fluorite-based sand, which reflects light particularly brilliantly, and which is found where granite rock has eroded. Such beaches are found elsewhere, for instance in Cornwall and parts of Scotland. Some of the Scottish colourists may have been familiar with similar beaches: perhaps an art expert could provide further illumination on this?

Dr Jacqui Stewart

Exeter

• I am impressed that Antoinette Sandbach MP feels she has to do the “right thing from time to time” (Dominic Grieve receives death threats after leading Tory rebellion, 15 December), making it clear what she thinks she is doing the rest of the time.

Ken Baldry

London

• John Haigh’s suggestion (Letters, 14 December) that Charles use the Latin fidei defensor has the added advantage that it was the original title (as bestowed by the pope).

Richard Watson

Cardiff

• While Mike Farley (Letters, 14 December) is heartened to know that temperatures care about us when they “struggle” to rise and keep us warm, I am less sanguine. Clouds “organise” to come between us and the sun and apparently last week in Scotland they were even “ganging up” on us. I wonder what evil plots the snow is hatching.

Rosemary Chamberlin

Bristol

• I feel quite sad when the shipping forecast tells me that a cold front is “losing its identity”.

Ruth Eversley

Paulton, Somerset

• I am not taking lectures on overpopulation from a bloke called Roger Plenty (Letters, 14 December).

Duncan Grant

London

• Join the debate – email guardian.letters@theguardian.com

• Read more Guardian letters – click here to visit gu.com/letters

• The first letter was amended on 22 December 2017 because the writer meant to refer to fluorite-based sand, not quartz-based sand.

