ON THE CONSTRUCTION OF THE HIGHLAND RAILWAY. 157 



which is now chiefly local since the opening of the Highland line. The cost 

 of the bridge, which is 660 feet long and 74 feet high from the foundations 

 to the top of the towers, constructed for a double line, was .£34,480 ; cost 

 per lineal foot £52 5s. The east abutment of this bridge is founded on rock, 

 and it was provided that the west abutment should be sunk and founded on 

 piles and a platform, the iirst imperfect trials having led to the conclusion 

 that there was nothing bej'ond indurated shingle at this place. On sinking 

 14 feet from the surface, however, through a conglomerate of boulders 2 to 

 3 feet in diameter, hard mountain clay appeared, and on penetrating this 

 for about 3 feet, rock was found, thus securing for this structure a rock 

 foundation on either side. Immediately at the east end of this viaduct, the 

 line, as already said, runs through a narrow and precipitous ravine, the 

 stream of which had to be diverted for the railway, by a new channel cut out 

 of the sohd gravel 30 feet wide, sloping longitudinally 1 in 40, and pitched 

 with stones from 12 to 18 inches deep. This pitching, which consists of squared 

 stones, had to a smaU extent broken up several times since the line was 

 opened ten years ago, from the floods bringing down stones and trees, and 

 we found that the most efl'ectual way of securing it was by inserting^walings 

 of timber 40 feet apart, 12 inches by 4 inches, across the channel, secured 

 at every 3 feet by iron piles, and grouting the joints of the pitching in dry 

 weather with lime-grout so as to prevent the lodgment of aii* and water, 

 which imder the pressure of floods has a tendency to dislocate the stone work. 



No. 10 is a viaduct crossing the Finclhorn, a dangerous and rapid river. 

 It sometimes comes down in great flood, almost in a body of 2 or 3 feet 

 of perpendicular height at a time, notwithstanding that in summer it is a 

 very moderate-sized stream. This bridge consists of three spans of 150 feet 

 each, with stone abutments and piers of solid ashlar, and is constructed for a 

 single line. There was no appearance of rock in the immediate neighbour- 

 hood of the site, although rock appeared on one side of the river about half 

 a mile above ; and the channel, as far as could be ascertained, consisted of 

 shingle and gravel. It was provided, therefore, that the foundation should 

 be sunk 6 feet below the deepest part of the bed of the river on a platform and 

 piles. The east abutment was so sunk, and the piles were driven through 

 the gravel to a depth of 10 feet, making 16 feet below the bed of the river. 

 It was observed that at that depth the piles uniformly would drive no further, 

 and this suggested the possibiHty of rock. Rock was accordingly searched 

 for, and it was found that about 18 feet under the bed of and across the 

 river, rock existed. Cofferdams were therefore formed, and rock foundations 

 were secuj'ed for the remaining piers and abutment. The cost of the bridge, 

 including a pitched embankment on the east side, the bottom of which was 

 secured by piles and a waling of timber, amounted — masonry to .£11,170 ; 

 ironwork =£10,260, making a total of .£21,430. Extreme length 608^ feet ; 

 height above foundations 46^ feet ; cost per lineal foot .£35 4s. M. 



No. 11 is a hi-idge across the River Nairn, consisting of four arches of 55 feet 

 span, and is an admirable piece of masonry. An incident connected with the 

 foundations of this bridge deserves to be mentioned. The contractor, when 

 instructed to ascertain the nature of the foundations, insisted that it was 

 unnecessary to take any trouble about them, as rock cropped out on either 

 bank ; the turnpike-road bridge across the river a quarter of a mile below 

 was founded on rock, and he said there could be no doubt that rock would 

 be got in the centre 3 or 4 feet below the bed of the river. Eock, however, 

 was not reached until we sunk from 13 to 14 feet, showing that experienced 

 persons may be misled even under the most convincing circumstances. The 

 structure, however, is founded on the solid rock throughout, and the cost for 



