A HISTORY OF LANCASHIRE 



over towards the coasts of Lancashire and north Wales it is very much greater, 

 and in the bays and estuaries of that side the stream is very rapid and the rise 

 of the water is very great. Thus at Liverpool the maximum velocity of the 

 stream in the River Mersey is from 7 to 8 knots per hour, and the maximum 

 tidal rise during spring tides is over 30 feet. 



It is due to these conditions that the gradient of depth in the Irish Sea 

 is much greater on the Irish than on the Lancashire side. Starting out from 

 (say) Dundrum Bay on the former side we encounter the 5O-fathom line at 

 about 1 5 miles from the coast, and long before we reach the Calf of Man we 

 are in water of about 80 fathoms in depth. But crossing from Fleet wood 

 towards the Calf, the gradient is very much less, and the average distance of 

 the lo-fathom line from the coast may be stated as about 10 miles. The 

 2o-fathom contour is about 20 to 30 miles from land, and between the 

 Lancashire and Manx coasts the greatest depth is not over 20 fathoms except 

 for one considerable depression. It is a credible hypothesis that Morecambe 

 Bay itself has resulted from the rapid eastward stream due to the meeting of 

 the north and south tidal streams, and however this may be it seems certain 

 that the shallow water area along the coast of Lancashire is due to erosion of 

 the coast-line in the past, and the distribution of the debris so formed by the 

 strong easterly and north-easterly tidal streams. The peculiarly evanescent 

 nature of the Lancashire coastal waters is due to the shallow sea so produced, 

 and to the great rise and fall of the tides. Twice a day practically the whole 

 of Morecambe Bay and great stretches of the Lancashire coast are laid bare 

 and become dry land. 



Sand is the characteristic bottom deposit in the sea off the coast of 

 Lancashire. Here and there the bottom consists of sand with varying pro- 

 portions of mud, and far out at sea we find extensive deposits of calcareous 

 matter, shells and comminuted fragments of the same, with material resulting 

 from the denudation of calcareous rock, also deposits formed by calcareous 

 algae. For the most part the Irish Sea bottom is clean sand or shelly gravel, 

 and affords good trawling ground. Only here and there do we find rough 

 ground on which the trawl net cannot be used. The greater portion of the 

 inshore sea bottom consists of sand or mud, with in places very restricted 

 patches of rough stones or gravel. 



We find as a result of the shallow seas and the rapid tidal streams that 

 the sea water off the Lancashire coasts hardly ever presents that pellucid 

 appearance which may be observed in the sea off a rocky coast, or far out from 

 land. The rapid tidal streams stir up the bottom and cause muddy particles 

 to be carried about in a state of suspension. River waters also carry down a 

 considerable amount of suspended inorganic matter to the sea. There are no 

 great rivers falling into the Irish Sea on the coast of Lancashire, but those 

 that do exist exercise a considerable influence on the specific gravity of the 

 sea water, which nowhere has the high density characteristic of truly oceanic 

 water. As a general rule the specific gravity is less than 1*026, and is often 

 very much less than that. Hydrometer readings of i -o 1 6 have been made in 

 the River Mersey off Liverpool landing stage, and readings of less than 1-020 

 in the Crosby Channel. On one occasion (Nov. 1904), I found the specific 

 gravity of the sea water a mile or two off Blackpool to be no more than 1*021. 

 About a week before this date there had been exceptionally high floods in 



