As of August 2017, the Royal Bank of Scotland is in the process of adopting a new series of banknotes. These will be made of polymer. Two (the £5 and £10 notes) have already been released, whilst a new £20 note is being designed. The £5 note shows Nan Shepherd on the obverse accompanied by a quote from her book 'The Living Mountain', and the Cairngorms in the background. The reverse displays two mackerel, with an excerpt from the poem (The Choice) by Scottish Gaelic poet Sorley MacLean. The obverse of the £10 note shows Mary Somerville, with a quote from her work 'The Connection of the Physical Sciences', and Burntisland beach in the background. The reverse displays two otters and an excerpt from the poem 'Moorings' by Norman MacCaig. The obverse of the £20 note, to be introduced in 2020, will show Catherine Cranston.