30 J. Waterliouse — An Account qftJ/e Tidal [No. 1, 



levelling with permanent bench-marks fixed in the ground in the vicinity of 

 the stations. 



The iron cylinders were made up in sections o£ 50 inches in length, a 

 sheet of wronght-iron being bent to the size required and rivetted to form 

 a cylinder, a cast-iron flange was fitted on to each end and the faces of these 

 carefully turned so as to fit exactly. The bottom section had a flat iron 

 plate carefully screwed on to one end, so as to form the bottom of the well, 

 and the whole when bolted together formed a water-tight well into which 

 water could only enter through the piping connecting it with the sea. The 

 size of the cylinders was decided on so as to utilise the iron sheets most 

 economically, and when finished four men could carry one section. Before 

 being let into the wells they were well painted over, inside and outside, with 

 tar in order to keep them from rusting. The level of the top flange of the 

 cylinder was about 6 feet above high-water spring tide, and about 2 feet 

 6 inches above the floor of the observatory. A board fitted on and screwed 

 to the toj) of the cylinder, with holes for the float-bands to pass through, 

 prevented anything falling accidentally inside the cylinder. 



The rigid iron piping was ordinary gas-pipe in lengths of about 14 feet, 

 with an internal diameter of 2 inches, which had been computed to be 

 sufficient to permit of the transmission of the tidal wave from the sea to 

 the cylinder in the well without sensible retardation, so that the height of 

 the water in the cylinder should always be the same as that of the surface 

 of the sea. In order to render the connections perfectly water-tight, as 

 well as to facilitate the joining together of the lengths of piping, these were 

 fitted with cast-iron flanges made to screw on to each end. 



The piping was connected with the bottom of the cylinder, at 9 inches 

 above it, by a small bend, and was then brought up vertically outside the 

 cylinder to a height 1 or 2 feet below the lowest high-water. At this 

 point was another bend with a stop- cock in it, and the pipe was then 

 taken straight out down to the sea along the slope of the shore to reach 

 low-water springs. 



The rigid and flexible pipes were connected together by means of the 

 following arrangement : 



To the end of the rigid iron pipe a brass connecting piece, made as 

 shown in the figure, was fitted, having two outer extremities, to one of which 

 a flexible two-inch suction-pipe was fixed and the other closed by a brass 

 disc with a good washer. When the flexible pipe had to be examined 

 for cleaning, the brass disc was unscrewed and a short length of spare flexible 

 piping with a rose at its end fitted on, and taken out to deep water tem- 

 porarily. The original pipe was then taken off and cleaned, the disc be- 

 ing screwed on for the time in its place ; then when finished the long pipe 

 and disc were replaced in their original positions. The flexible pipe was 



