A good example of this technique can be seen in "Trancept of Ewenny Priory, Glamorganshire", painted in about 1797 and on display at the Royal Academy's exhibition Turner: the great watercolours.
Next year is the 150th anniversary of Turner's death and, although Turners can always be seen in large numbers at Tate Britain, this smaller exhibition is a delightful introduction to the work of Britain's best-known painter - perhaps the most outstanding tonalist anywhere.
Joseph Mallord William Turner wasted no time starting his career. He exhibited for the first time when he was only 15, in 1790, and at 26 was the youngest academician ever. He produced more than 1,800 watercolours at all stages of his life, some of them as book illustrations, some to serve as the basis for prints, some on commission or in response to buildings and landscapes in Great Britain and Europe.
He wasn't a visual reporter so much as an idealist, and there are many cases of landscapes being "improved" to meet his preferences. He was an inveterate traveller, making trips to Wales and Scotland as well as France, Switzerland, the Rhineland and Italy.
The Ewenny Priory watercolour might be mistaken for a charming, romantic scene, until you spot the chickens in the nave and the air of neglect. This, says Royal Academy co-curator Eric Shanes, is Turner's way of commenting on the destructiveness of the Reformation.
Turner's technical brilliance is matched by his observation of life in the 18th and early 19th century and his interest in the most important political debate of his day, parliamentary reform. But the theme for which he is best known - the puniness of humankind when set against the power and magnificence of nature - is thoroughly represented in the Royal Academy exhibition.
"The Blue Rigi, Lake of Lucerne, Sunrise 1842" is regarded by some as the finest example of Turner's work as a tonalist. It has a quiet humour too - a scene of peace and light is the setting for noisy hunters with their guns.
Family workshops for adults and children aged 12-16 will take place on December 19 and 21, and a student seminar is planned for January 17. Schools and colleges can arrange guided tours with a gallery educator for groups of 10 or more students and primary and secondary children can attend workshops.
For information about events and how to obtain a free, colour-illustrated teachers' pack, tel: 020 7300 8000. www.royalacademy. org.uk Another London landmark building has been transformed - and all for the benefit of education. The Queen Elzabeth II Great Court at the British Museum is a vast, elegantly covered area with a glass roof that looks like a modern take on medieval fan vaulting.
In the centre is an extraordinary white circular structure, a bastion with steps sweeping up at either side. This is the famous domed reading room, visible externally for the first time. Inside, its ceiling delicately picked out in pale blue and gold, it is as exciting a place to enter as it was when you might have bumped into Lady Antonia Fraser or Jeremy Paxman researching their latest great work.
There are still books on the shelves around the circle (most are at the new British Library at St Pancras) but one innovation strange to old-style readers here is carpet. The reverberating echo, enough to wake the drowsiest academic, has gone.
The reading room itself will be used for educational activities and there are lecture rooms, an ICT suite, workshop and handling spaces beneath. A whole school could get lost in here. The limestone may be, according to some newspapers, second-rate, but look out for the little ammonite in the slab just at the bottom of the steps down to the workshop spaces. A programme of study days and workshops is planned. Information: 020 7323 85118854. www.thebritishmuseum.ac.uk Theatre Alibi's humorous show for five to 12-year-olds, In One Ear and Out the Other, will continue to tour schools in Devon until the end of term.
One more public performance is set for tonight, at Alphington combined primary school, Exeter. The company (and two others, Pop-up Theatre and the West Yorkshire Playhouse) has just won pound;45,000 under the Sainsbury's Checkout scheme to encourage new theatre writing for children. Its Why the Whales Came, for nine to 13-year-olds, based on the book by prize-winning author Michael Morpurgo, will open at the Theatre Royal, Plymouth, next autumn before touring nationally. It is a magical story about an abandoned island in the Isles of Scilly with a secret uncovered by two children.
Information about Theatre Alibi: 01392 217315.
The Christmas holidays are almost here. London's Theatre Museum is putting on workshops about pantomime (information: 020 7943 4700) and museums and galleries everywhere are entering the snowflake and tinsel zone.
Pantomime has enormous appeal still and it is possible to discover traditional ones among the vehicles for television personalities and pop stars. Roy Hudd is an authority on Victorian music hall. Aladdin playing until January 13 at the Palace Theatre, Watford, written by him, is likely to be a gem. Tickets: 01923 225671.
Dylan Thomas' s A Child's Christmas in Wales, full of domestic embarrassments, misbehaving uncles, carols and tweedy nostalgia, is at the end of its tour in Theatr na n'Og's production but will be at the Bloomsbury Theatre in London between December 12 and 16. Tickets: 020 7388 8822.