"Oh Tom! Such a gas has Davy discovered, this gaseous oxide. Oh Tom! I have had some. It made me laugh and tingle in every toe and finger tip. Davy has actually invented a new pleasure, for which language has no name. Oh Tom! I am going for more this evening! It makes one strong and happy! So gloriously happy!"

Coleridge also took the gas (as well as experimenting with Davy in the use of cannabis), which gave him, he wrote, "more unhinged pleasure than I had ever before experienced". It caused him to create the new word "psychosomatic". He and Southey had earlier talked of founding a utopian "pantisocracy" on the banks of the Susquehanna River in what is now upstate New York. Now he decided that science was the real utopia which they must all build together, and he urged Davy to come to the Lake District, and build a new poetical-chemical institute there.

Instead, Davy was summoned to London by the great organising panjandrum of British science, Sir Joseph Banks, about whom Holmes has much to say. He transformed Davy from a provincial performer into a metropolitan star, whose lectures, attended by duchesses and leading politicians, created some of London's first traffic jams.

Nevertheless, the Lake District played a notable part: in 1805 we find Davy climbing Helvellyn in the company of Robert Southey, William Wordsworth and Sir Walter Scott. On the summit, they talked of Coleridge, then absorbing Kantean philosophy in Germany. The District produced some brilliant empirics, and I wish Holmes had devoted more space to it and them. He mentions John Dalton, author of the New System of Chemical Philosophy (1808), who laid the foundations of the modern oil and petrochemical industries, but thinks he came from Manchester. It is true he lectured at Manchester New College for 30 years, and was buried there. But he was born in Eaglesfield, near Wordsworth's home town, Cockermouth, and much of his observational work was carried out on the Cumberland hills. He always took with him a big thermometer and a theodolite, sometimes even heavier equipment, carried on a donkey. In July 1812, on the top of Skiddaw, he met two more local, self-taught scientists, Wilson Sutton and Jonathan Otley. Sutton was so impressed by the speed with which Dalton climbed that he said: "John, I wonder what thy legs are made of." Of course, Wordsworth had astounding legs for climbing too, as a famous passage in Thomas De Quincey makes clear. It is odd that Holmes does not mention Sutton and Otley, especially the latter, for Otley, self-taught like Dalton, was a superb geologist, who first worked out the complex rock structure of the Lake District. He produced the first accurate map (1819) and the pioneering Concise Description of the English Lakes and Adjacent Mountains (1824), both invaluable to Wordsworth's later book on the subject.