IN THE MONTH OF FEBRUARY, 1852. 189 



The ground was first broken for the construction of this 

 reservoir in September, 1848 ; and, in the following month, 

 before much progress had been made, a very heavy flood 

 occurred in the neighbourhood of Blackburn, which was the 

 cause of a lamentable accident at Darv^^en, near that town, by 

 the bursting of a private reservoir and the consequent loss of 

 twelve or thirteen lives. The volume of this flood I was 

 enabled to determine with tolerable approximation to accu- 

 racy, by means of the reservoirs of the Blackburn waterworks, 

 which were then just completed. It exceeded 25 feet per 

 second for every 100 acres of collecting ground. Had a 

 similar heavy fall of rain occurred in the upper part of the 

 Longdendale district, it would have produced a flood of about 

 2,000 cubic feet per second at the Woodhead Reservoir, — 

 nearly double the volume which had been provided for. 



Acting upon the experience and information thus acquired, 

 an additional discharge pipe was immediately introduced, and 

 the flood watercourse was enlarged as far as practicable, so 

 that a flood of 1,500 feet per second could be passed with 

 safety, with 16 feet of pressure upon the pipes. As the em- 

 bankment gradually exceeded that height in the course of 

 construction, the means of storage behind the banks would be 

 increased ; and by the greater pressure upon the pipes more 

 water also could be discharged, and in these ways provision 

 would be made for the safe passage of a still larger quantity. 

 On several occasions, in the course of the following eight or 

 ten months, the floods amounted to 1,800 or 2,000 feet per 

 second ; shewing the wisdom, and indeed the necessity of 

 such a provision having been made. 



Early in October, 1849, just twelve months after the 

 Blackburn flood, which bad aflcirded such valuable information, 

 the flood watercourse having been completed, the discharge 

 pipes laid, and every arrangement made for proceeding with 

 the embankment of the reservoir, the inner tie of that bank 

 was raised to a height of about 16 feot, so as to give that 



