IV

PREFACE.

bridge, of only one arch, proposed to be thrown over theriver Thames at London ; with several other appropriate ar-ticles, as below.

Tract ii, exhibits some curious queries concerning Lon-don Bridge, proposed in the year 1746 by the magistrates ofthe city; with the ingenious answers given to the same, byMr. George Dance, surveyor-general of the city works, beingthe result of that gentleman’s' examination concerning thestate of the bridge at that time.

Tract hi contains experiments and observations to bemade on the state of London bridge; being the report of acommittee of the members of the Royal Society, addressed tothe common council of the city of London.

T ract tv treats of the effects which might be producedon the tides in the river Thames, in consequence of erectinga bridge at Blackfriars. This was an ingenious report, drawnup by the late Mr. John Robertson, at the request of the cityof London.

Tract v consists of answers, given by me, to questionsproposed by the Select Committee of Parliament, relative toa proposal, made by Messrs. Telford and Douglas, for erect-ing a new iron bridge, of a single arch only, over the riverThames, instead of the present London bridge.

Tract vi exhibits a brief history of the original invention,and subsequent improvements of iron bridges, as practisedof late years in this country.

Tract vii is a dissertation on the nature and value of in-finite series; explaining the properties of several forms ofsuch series, as converging, diverging, and neutral.

Tract viii is a new method for the valuation of numeralinfinite series, that have their terms alternately plus andminus; which is performed by taking continual arithmeticalmeans between the successive sums, and between the means ;a method bv which the value or sum of any such series is veryeasily and quickly obtained.