G.—ENGINEERING 119 
Such contradictory statements made by those who set out to be authori- 
ties on the subject were of little help to engineers or architects who had to 
take the responsibility for the actual building of an arch. The effect of 
the conflicting ideas can be illustrated by reference to Blackfriars bridge 
in Norwich. It is the first of the only two bridges known to have been 
designed and built by Sir John Soane, the architect of the Bank of England. 
It is a single arch bridge and was built in 1783. The contractor was 
John de Carle, stonemason of Norwich. Sir John Soane’s specifica- 
tion describing the method to be adopted in constructing the bridge is 
preserved. 
Although the Portland stone arch is of ample proportions, the architect 
appears to have had little confidence in the simple arch principle, and as 
will be gathered from the following extracts, he required the masonry 
of the bridge to be cramped and fastened together with iron in every 
possible way, so as to eliminate all possible risks of failure. 
“To build the Arch with Portland Stone, the Voussoirs of which it is to be 
constructed, are to be of the Number, form, Workmanship and Dimensions 
expressed in the Drawings : the Arch Joints are to be wrought exceedingly 
true and exact and be perfectly smooth and to be set dry in Milld Lead of four 
pounds to the foot and in order to prevent flushing the extremities of the 
said Joints next the Soffite of the Arch are to be flarched off and pointed 
up after the Center is struck as shall be directed. In the middle of each 
joint of each Voussoir is to be inserted two Cubes of Cast Iron of the weight 
of three Pounds each let equally into each Stone, and Channels are to be 
sunk from the Tails of the Voussoirs to the cavities for the Iron Joggles and 
the said Cavities and Channels are to be run full of lead.’ 
“To provide and fix four Tyes or Chain Bars across the Bridge in the 
Positions marked in the drawing of Swedish Iron three Inches broad and 
three quarters of an inch thick with strong Corkings at each end to lay 
hold of 4 other bars each nine feet long and one inch square to be let down 
into the Ashler and fixed therein with Lead.’ 
‘To cramp all the Cross Joints of the Key Course and in the Arch joints 
thereof are to be twelve Joggles to consist of Bent Hooks nails staples and 
other Irregular Pieces of Small Iron filled and crammed into Dovetail 
holes to be cut into the Arch Joints of the Key Course and these adjoining 
of the two next Courses down to the middles of the Stones and to Run the 
same with Lead.’ 
Some years ago I inspected and reported on this bridge. I found it 
in very good condition. ‘There was little, if any, evidence of the cramps. 
It was to be expected that their corrosion would have burst pieces off the 
masonry but in this instance the iron must have been very effectively 
protected from moisture or the architect may have finally decided to leave 
much of it out: it certainly could not have added appreciably to the 
stability. Many fine buildings have suffered badly from the corrosion of 
iron cramps. For many years architects and builders of the past were 
extraordinarily lavish in their use of cramps. ‘They put them in plain 
ashlar walls and places where they could have had no beneficial effect. 
The obsession for cramps in masonry is very like the present tendency to 
embed steel in all concrete. Concrete properly reinforced, is an admirable 
material for construction, but large masses of concrete frequently have 
