218 REPORT— 1869. 



thau the foundations. In nine cases out of ten it would be better to brealc up all 

 raised floorings, and throw tlie material round the pier foundations, rather than 

 give a plunging direction to the water down-stream. 



If this view be correct, it at once proves that with loose sand to unknown depths, 

 the only safe mode for bridging the large rivers is to have deep foundations, which 

 necessitate great spans, and iron girder jjridges, and as the sand pump makes the 

 sinking such a simple matter now, the difference of 10 feet more or less of depth 

 in cost is insiguihcant. (In Madras, where there is an imlimitod supply of heavy 

 material, the ease may be different, and there shallow foundations may be more 

 economical.) An extra depth of 10 feet or so, however, is nearly tantamount to 

 doubling the sectional area of the watei-way, and as water does not move in straight 

 lines, it matters little what the shape of tlie section may be when passing through 

 a bridge ; thus the waterway may be doubled without adding to the breadth, but 

 by deepening the bed. By this means, without adding much to the cost of a bridge, 

 not only the main stream, but also the inundation water could all be passed through 

 the one bridge, and thus a great saving effected b}' having no flood-openings, and 

 consequently no danger of the main river taking to these side openings, while the 

 only inconvenience would be to cause tbe flood to last a few hours longer than it 

 otherwise would. 



But, however, where the embankment crossing a valley is of a great length, all 

 the water could not drain back to the main stream, after the flood had passed ofl', par- 

 ticularly when, as has been already shown, the gTOund is much lower away back from 

 the river than at its banks. To get rid of this Avater, siphons with spoon-mouthed 

 openings at both ends should be jirovided, so that though the water could rush 

 through the greater length of the siphon at a velocity of even 10 feet a second, yet 

 it would approach and leave the siphon at the natural velocity of perhaps not more 

 than 2 feet a second. Thus no violent action could take place either above or 

 below, and at the points of admission and egress, the water would have the proper 

 load of silt due to its velocity. 



From all the author has read, seen, and heard, he cannot help thinking that a 

 large proportion of the late accidents on works in India is to be attributed to the 

 causes assigned in this paper, namely, an excessi\'e velocity given to a stream that 

 has already been partialh- depri\ed of its natural load of earthy matter, thereby 

 causing a violent action below, and sometimes even above bridge. 



The importance of the questions now raised as to bridging rivers in India is 

 daily becoming greater ; for, while this paper was being prepared, the Government 

 of India has determined to construct the Lahore and Peshawur IJailway, which 

 line must cross, not onlj^ the Ravee, the Chanab, and the .Ihiluni, but "also the 

 Indus passing over the IMchna Doab, which has been described above. Should, 

 therefore, the suggestions now made be con-ect, it is evident that hundreds of 

 thousands of poimds may be saved by adopting them, and thus, a proper knowledge 

 of these laws arri^x'd at, may enable the engineer to make this line of railway, 

 which is supposed to be one of the most difficult lines to construct in India, with 

 perfect confidence of success, and at possibl}' less cost than many of those now 

 constructed. 



The author would only now add, that the knowledge of the abrading and tran- 

 sporting power of water is not only desirable in designing roads, railway's, or canals, 

 but affects every question connected -wiih hydraulic works in all countries. It 

 would occupy too much time to allude to them further; but he may, ho-\\-ever, venture 

 to ask what would be the fluancial state of Southern India (which now does not 

 pay) if harbours were constructed on sound principles, so as not to be silted up ? 



Time -will not admit of the author's describing a modilication of the siphons, 

 which he thinks, in some instances, may be introduced with ecimomy for crossing 

 minor streams, instead of bridging them in the usual manner ; but ho believes not 

 only can this be done with advantage, biit also, with spoon-mouthed siphons, 

 in Bengal inundatioij. water may be carried through embankments in regulated 

 volumes, so as to be aya^hible for irrigation, thus adding both to the fertility of 

 the soil and the salubrity ^i! the climate, while the embankments would protect 

 the country from those devastating floods which so often destroy both life and 

 ^property. 



