In 1840 Cautley reported on the proposed Ganges canal, for the irrigation of the country between the rivers Ganges, Hindan and Yamuna, which was his most important work. Cautley began working towards his dream of building a Ganges canal, and spent six months walking and riding through the area taking each measurement himself. He was confident that a 500-kilometre canal was feasible. There were many obstacles and objections to his project, mostly financial, but Cautley persevered and eventually persuaded the British East India Company to back him. This project was sanctioned in 1841, but the work was not begun till 1843, and even then Cautley found himself hampered in its execution by the opposition of Lord Ellenborough. Digging of the canal began in April 1842. Cautley had to make his own bricks, brick kiln and mortar. Initially, he was opposed by the Hindu priests at Haridwar, who felt that the waters of the holy river Ganges would be imprisoned; but Cautley pacified them by agreeing to leave a gap in the dam from where the water could flow unchecked. He further appeased the priests by undertaking the repair of bathing ghats along the river. He also inaugurated the dam by the worship of Lord Ganesh, the god of good beginnings. Construction of the dam faced many complications, including the problem of the mountainous streams that threatened the canal. Near Roorkee, the land fell away sharply and Cautley had to build an aqueduct to carry the canal for half a kilometre. As a result, at Roorkee the canal is 25 metres higher than the original river. From 1845 to 1848 he was absent in England owing to ill-health, and on his return to India he was appointed director of canals in the North-Western Provinces. When the canal formally opened on 8 April 1854, its main channel was long, its branches long and the various tributaries over long. Over in 5,000 villages were irrigated. He was also instrumental in the establishment of the Roorkee college, named the Thomason College of Civil Engineering in 1854 and now known as IIT Roorkee. One of the twelve student hostels of IIT Roorkee is named after him.
While the first canal in Dehradun was laid in the 17th century, Cautley significantly expanded the network in the 1850s. Five canals were laid in the city that irrigated the surrounding villages and produced a cooler microclimate. Since 2000, when the city became the state capital, most of the heritage canal network has been covered or demolished to expand the roads for ever-increasing traffic.
Fossil work
Cautley was actively involved in Dr Hugh Falconer's fossil expeditions in the Siwalik Hills. He presented a large collection of mammalian fossils, including hippopotamus and crocodile fossils indicating that the area had once been a swampland. Other animal remains that he found here included the sabre-toothed tiger, Elephis ganesa, the bones of a fossil ostrich and the remains of giant cranes and tortoises. He also contributed numerous memoirs, some written in collaboration with Falconer, to the Proceedings of the Bengal Asiatic Society and the Geological Society of London on the geology and fossil remains of the Sivalik Hills.
Writings
Cautley's writings indicated his large and varied interests. He wrote on a submerged city, twenty feet underground, in the Doab: on the coal and lignite in the Himalayas; on gold washings in the Siwaliks, between the Sutlej and the Yamuna; on a new species of snake; on the mastodons of the Siwaliks and on the manufacture of tar. In 1860 he published a full account of the making of the Ganges canal.
After the Ganges canal was opened in 1854 he went back to England, where he was made KCB, and from 1858 to 1868 he occupied a seat on the Council of India. He died at Sydenham, near London, on 25 January 1871.
