OHAP. IX. milNDLKVS LAST CANALS. 457 



profession, and tin- givat authority on all questions of 

 navigation, lie was, in 1770, employed by the Corpora- 

 tion of London to make a survey of the Thames above 

 I>attrrsra. with the object of having it improved for 

 purposes of navigation. As usual, Brindley strongly 

 recommended the eonstruction of a canal in preference 

 to carrying 011 the navigation by the river, where it was 

 liable to be interrupted by the tides and floods, or by 

 the varying deposits of silt in the shallow places. In his 

 first report to the Common Council, dated the 16th of 

 June, 1770, he pointed out that the cost of hauling the 

 barges was greatly in favour of the canal. For example, 

 he stated that the expense of taking a vessel of 100 or 

 120 tons from Isleworth to Sunning, and back again 

 to Isleworth, was 80., and sometimes more ; whilst the 

 cost by the canal would only be 16. The saving in 

 time would be still greater, for the double voyage might 

 easily be performed in fifteen hours ; whereas by the 

 river the boats were sometimes three weeks in going 

 up, and almost as much in coming down. He esti- 

 mated that there would be a saving to the public of at 

 least 64/. on every voyage, besides the saving of time in 

 performing it. After making a further detailed exa- 

 mination of the district, and maturing his views on the 

 whole subject, he sent in a report, accompanied by a 

 profile of the river about seven feet long. We quote 

 the document, which is little known, as a specimen of 

 P)i indley's reports, though doubtless written by a more 

 practised hand : 



" To THE COMMITTEE OF THE COMMON COUNCIL OF THE CITY OF 



LONDON. 



" GENTLEMEN, Pursuant to your instructions, dated 27th July, 

 1770, I have made a survey of the River Thames from Boulter's 

 Lock to Mortlake in Surrey, and have made a plan and profile of the 

 same, with a level and fall line, remarking the different falls from 

 one town to another ; and likewise have examined the most material 

 obstructions and inconveniences that attend the present navigation, 



