He travelled into Scotland to commune with the honourable John Napier of Merchiston about making the logarithmical tables.
Looking once on the map of England, he observes that the two rivers, the Thames and that Avon which runs to Bath and so to Bristol, were not far distant, i.e. about 3 miles -- see the map. He sees 'twas but about 25 miles from Oxford; gets a horse and views it and finds it to be a level ground and easy to be digged. Then he considers the charge of cutting between them and the convenience of making a marriage between those rivers which would be of great consequence for cheap and safe carrying of goods between London and Bristol, and though the boats go slowly and with meanders, yet considering they go day and night, they would be at their journey's end almost as soon as the waggons, which are often overthrown and liquors spilt and other goods broken. Not long after this he died and the civil wars broke out. It happened by good luck that one Mr Matthews of Dorset had some acquaintance with this Mr Briggs and had heard him discourse on it. He was an honest simple man, and had spent all his inheritance, and this project did much run in his head. He wanted to revive it (or else it had been lost and forgotten) and went into the country to make an ill survey of it (which he printed) but with no great encouragement from the people of the country or others. Upon the restoration of King Charles II, he renewed his design, and applied himself to the king and council. His majesty espoused it more (he told me) than anyone else. In short, for want of management and his non-ability, it came to nothing and he is now dead of old age. But Sir Jonas Moore (an expert mathematician and a practical man) being sent to survey the manor of Dauntsey in Wilts (which was forfeited to the crown by Sir John Danvers's foolery), went to see these streams and distances. He told me the streams were too small except in winter; but if some prince or the parliament would raise money to cut through the hill by Wooton Bassett, then there would be water enough and streams big enough. He worked out the cost, which I have forgotten, but I think it was about £200,000.