70 Kepokt 8.A.A. Advanckmext of 8cien'ce. 



properly surruuud the reinforcing inetal witli a dry mixture, more 

 water is necessar}', in which case the moulds should be water-tight. 



It has been stated by some authors that the reinforcing metal 

 should be clean and quite free from rust before being embedded in 

 the concrete, but practice has proved this to be unnecessary as long 

 as the metal is not scaled. It is, liowever, advisable to brush the 

 metal with grout before being emliedded. 



Besides the careful selection, proportioning mixture and rannning 

 materials, the design and placing of reinforcement, the greatest vigi- 

 lance must be exercised during the erection and removal of stagings, 

 centres, moulds and shuttering. Neglect of any of these operations 

 may endanger the safet}' of a structure. 



Dui'ing the construction of some important reinforced concrete 

 works accidents liave occurred, but most of these ha\e been traced to 

 careless workmen, either allowing foreign material, such as sawdust, 

 shavings or blocks of wood, to get into the moulds of columns f)r beams, 

 and neglecting to remove same before the concrete is put in, the 

 premature removal of suj^ports before the concrete is properly set, or 

 an omission of an important member of a reinforcement. It is, how- 

 e^■er, satisfactory to learn that few accidents have occurred of late 

 years. 



Rpinforced Concrefp (Jon^tructioit in the Cape Colcmy. — Reinforced 

 concrete has been little used in the Cape Colony, the first examples 

 being in the form of beams, columns, and flu(.>rs to buildings : and in 

 most of these cases, as a substitute for steel framing, joists and wooden 

 flooring, it has been found by architects to be more economical as well 

 as safer against fire. 



The more recent works are as follows :-- 



Columns and roof of the Kloof Nek service reservoir. 

 Service reservoir at Port Elizabeth. 

 Robben Island jetty head. 

 "Henry Putt" bridge at Port Alfred. 

 As the twt) latter works were under the author's personal supervision,, 

 a short description of the same may not come amiss. 



RohJieii Island Jettij Head. — This jetty, originally built vi steel 

 rails braced and ri vetted, is 600 ft. long and 15 ft. wide, excepting the 

 head, which occupies 45 ft. of the abo\ e length and is 20 ft. wide. It 

 was constructed by the Public ^^'orks Department in 1S95, but owing 

 to the destructive action of the sea-air and salt water many of the 

 supports and bracings have been destroyed in such a way as to weaken 

 the structure. 



In 1907, owing to the dangerous condition of the head of the 

 jetty during landing and shipping operations, it was decided by the 

 Government to reconstruct the same. The first intention was to use 

 steel girders for the superstructure, founded upon steel cylinders filled 

 with concrete, but ultimately it was decided that reinforced concrete 

 should be employed instead. Tiie bottom upoii which the jetty is 

 built is (»f rock, into which three steel dowels were fixed at each point 

 where tiie uprights of the sujierstructure occurred. These groups of 



