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department. They consist of cement blocks, pierced with a varying 

 number of circular ducts, 75 millimeters in diameter. The blocks, 

 which are from one to one and a half meters in length, are laid 

 in the ground with the joints resting on cement base pieces of 

 trough form, which keep them truly end- to end.. The blocks are 

 made with three longitudinal depressions or furrows, into which, 

 after the blocks are laid, strong iron bars are fitted. Thin plates 

 of bitumen, having circular holes corresponding to the ducts, are 

 placed between the blocks, several of which are forcibly clamped 

 together, end to end, so as to compress the bitumen plates. The 

 furrows containing the iron bars are then filled with cement, which, 

 when set, binds the blocks rigidly together. Section after section 

 is thus treated until a very solid conduit is produced, which, with 

 the earth removed from beneath, is said to bear a direct weight 

 of two tons without collapsing. The joints are made finally tight 

 either with bitumen or cement. The ducts are made to correspond 

 prior to clamping by inserting round rods made to fill them accu- 

 rately through the blocks under treatment, the rods being with- 

 drawn when the cement has set. No difficulty is stated to be ex- 

 perienced in obtaining correspondence between the ducts or in 

 subsequently drawing in cable of a diameter of 52 millimeters to 

 a length of 200 meters. The joints are said to be perfectly water- 

 and gas-tight. The details of this system are made clear in 

 fig. 130, in which M 1 M 2 M 3 are respectively cross, longitudinal, 

 and horizontal sections of a concrete manhole with conduits and 

 cables in position. The conduits are shown in cross-section at 

 c l c 2 , while B B B represent three blocks jointed together, as de- 

 scribed, at j j, T T being the cement base pieces and R R the iron 

 clamping rods. D D 2 D 3 are corresponding views of a draw-box 

 adapted for a five-duct conduit. The General Company's conduit, 

 while being essentially of the same construction, differs somewhat 

 in form, the cross-section being as shown in fig. 131, with the iron 

 rods passed through channels R R R R made in the interior instead 

 of on the exterior of the blocks. Mr. Hultmann has unquestionably 

 produced a strong and efficient conduit which has already stood 

 the test of several years' service most successfully. The separate 

 duct plan is almost essential to underground cable work, as it 

 enables repairs and alterations to be carried out easily, which 



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