24 



of the t\-pe than to faulty construction or appHcation of the method. It is safe to say 

 that many of the "faihires" could he successful if faulty workmanship and application 

 could be avoided. 



THE MODERN PERIOD: IMPROVED PRACTICE IN ALL DIRECTIONS 



In the decade beginning in 1908, attention continued to be focussed on the possi- 

 bilities of concrete in one form or another, culminating in the present day use of rein- 

 forced concrete; but its latter half also saw a return of creosote to popular favor for 

 marine structures. 



In 1908 a modification of the Holmes c>'linder was de\-eloped which in part 

 eliminated some of the difficulties previously experienced. In this type the three-pile 

 cluster was replaced by a single pile, encased in concrete. With the single-pile type 

 it was possible in construction to place around the pile a gasket which sealed the 

 bottom of the form, after which the form could be pumped out and the concrete 

 poured properly. This type has given excellent service to date. 



The Koetitz form of precast concrete casing for timber piles was also developed 

 in 1908. In this type the casing is cast on land and, after curing, is slid over the previ- 



f~ig. 10, Driving cylindrical cofferdam lurnis, pier ib, August, V)W. 



{Board of Stale Harbor Coins. Photo.) 



ously driven pile, in place, the space between being filled with sand or grout. This 

 protection has proved very successful, although never extensively used on account of 

 rather high cost. Another development of the year 1908 was the Black's Patent, which 

 was the forerunner of several forms of pile repair now used for salvaging piles in place, 

 by pouring around each a concrete jacket, section by section, without contact with 

 surrounding water until after the concrete has been poured. That same year there 

 was introduced also a substructure unit in which piles were omitted, consisting of a 

 reinforced concrete column cast in place in a large cylindrical coffer dam previously 

 driven to hard bottom and pumped dry. In both types the forms were afterwards 

 pulled and used elsewhere. The latter type could only be used where the distance to 

 hard substrata was within the practical limit in length of the cylinder forms. With 

 the exception of minor defects, the type has given good service. 



