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TRACT IV.

OX THE CONSEQUENCES TO THE TIDES IN THE RIVER

THAMES, BY ERECTING A NEW BRIDGE AT LONDON.

BY MR. JOHN ROBERTSON.

WHILE it was in contemplation to erect tlie new bridgeover the river at Blackfriars, there was much public conversa-tion and speculation on the probable effects of such erection,relative to the tides in the river, and other matters connectedwith it. On this occasion, the magistrates of the city ofLondon consulted many scientific men and practical engi-neers, touching those points. Among others, they requestedthe advice and opinion of Mr. John Robertson, then masterof the Royal Mathematical School in Christ’s Hospital, by aspecial letter from the Town Clerk, as follows.

“ To Mr. Robertson at Christ's Hospital.

tl Sir,—The Committee of Common Council appointed toconsider, whether the Navigation of the river Thames willin any and what manner be affected by a new Bridge, intendto meet at Guildhall, on Thursday the 12th instant, at 10o’clock in the forenoon, and desire you will be so kind as tofavour them with your company at that time, in order to givethem your opinion and assistance therein. I am, Sir,

“ Your most obedient, humble Servant,

“ James Dobson.”

Town Clerk’s Office, Guildhall, 5 Dec. 1T54.

Mr. Robertson's Answer.

“ Before I deliver my opinion concerning the questionproposed, 1 think it necessary to premise some few principles