158 REPORT— 1867. 



a double line was £8620. Length 371 feet ; height 56 feet ; cost per 

 Kneal foot £23 4s. 8d. 



No. 12 is a viaduct across the Ness, consisting of five arches of 73 feet span 

 over the river, 4 land arches of 20 feet span, and 2 cast-iron openings 

 of 27 and 35 feet span over roads. The foundations of this bridge, as in 

 many others, consisted of shingle for 20 feet down, but at the north abut- 

 ment and pier tlie iron rods driven in appeared to penetrate considerably 

 easier than at other points of the channel, and it was deemed prudent to 

 construct this abutment and pier upon bearing piles and a platform, and 

 they were accordingly so done, as exhibited in the drawings. The total 

 length of this bridge, including the side arches, is 669 feet, and the total 

 height from the bed of the river to the top of the parapet is 40 feet. It is 

 constructed for a single line, and cost £13,410. Cost per lineal foot =£20. 



No. 13 is a good example of a siuing bridge built across the Caledonian 

 Canal, which the line spans on a skew of 65 degrees. It consists of 2 

 girders of 126 feet in length, 78 feet of which, from the centre of the turn- 

 table, spans the canal, and the remaining 48 feet forms the balance weight. 

 Advantage was taken of the canal being emptied for repaii-s to lay the foun- 

 dations of the masonry, which are on a platform and piles in the sohd gravel, 

 9 feet below the surface of the water. The depth of the canal is 18 feet, 

 and the width of the locks 40 feet, the canal banks being 120 feet apart. 

 Some difficulty occurred at first during hot weather from the expansion of 

 the iron aff'ecting the adjustment and closing of the bridge, which was 

 remedied by means of a powerful screw, and the bridge has been worked with 

 satisfaction and safety for the last five years. This bridge, with its machinery, 

 timber, wharves for protection from vessels, distant and station signals, &c., 

 complete, cost £4718. 



No. 14 spans the River Conon in Ross-shire. From peculiar circumstances 

 it was necessary that this bridge should cross the river on a skew of 45 

 degrees to the stream, and as there were rock foundations, there was no 

 difficulty to contend with beyond that of 4 or 5 feet of water in the channel 

 of the river to reach the rock, which was successfully accomplished. The 

 peculiarity of the skew with the river at this place would have been more 

 easily provided for by the adoption of iron girders from pier to pier, but 

 as the writer found at that time that iron girders would be fully as expen- 

 sive, and not so permanent as a stone bridge, and as there were admirable 

 quarries in the neighbourhood, he resolved to construct this bridge, as already 

 said, on a skew of 45 degrees with the river, by a series of right-angled ribs 

 or arches spanning from pier to pier. This is no new arrangement ; but the 

 writer is not aware of the plan being adopted for a series of arches of so 

 large a span in any previous instance. The bridge consists of 5 arches of 

 73 feet span each, the arches being constructed of four ribs, each 3 feet 9 

 inches wide ; the arch-stones are 4 feet deep at the springing, and 3 feet 

 deep at the crown. The keystones of the centre part of each arch were made 

 to connect with each other, as were the stones in the haunchings of the 

 arches, and some cramps of iron were inserted at the joints to connect the 

 ribs. The work was successfully accomplished, and constitutes a very perfect 

 piece of bridge masonry. The total length of the bridge is 540 feet, and the 

 height 45 feet from the bed of the river. The north abutment is founded 

 304 feet lower down the river than the south, and the whole structure, when 

 the centres were removed, was found so accurately built that no joint in it 

 showed any indication of setting. The cost of this bridge for a single line 

 was £11,391. Cost per lineal foot £21 2s. 



There are many other bridges, as may be supposed, over so great an extent 



