TRANSACTIONS OF SECTION E. 429 



in 1859 to 38 in 1861; and at Barnsley, within the Don valley, there was an 

 extraordinary difference between the annual rainfalls of two succeeding years, 

 namely, 42 inches in 1872, and 16 in 1873. The latter example shows the 

 necessity for a series of observations extending over many years. The geographer, 

 in his meteorological researches, should not of course neglect registration. On the 

 contrary, he should be habitually exact on this point ; but he should be careful, at 

 the same time, to collect all kinds of information respecting normal and abnormal 

 seasons, and all other particulars which might serve both to supplement and to 

 check his observations. 



In all these branches of the subject the comparative elements should be kept 

 in view. We must look back as far as the records of history will allow us, to 

 learn the causes of the present state of the surface of our district, from its past 

 condition at various historical epochs. It is here that the historian and the topo- 

 grapher come to our aid. Time is a powerful and active agent in these changes ; 

 but the most interesting and instructive side of the subject is the examination of 

 the effects of human agency in the changes on the earth's surface. 



From this point of view the histoiy of a mountain range frequently offers a 

 most valuable subject for study. Mountains usually supply within themselves a 

 natural regulator which checks the rapid flow of the rain water in surface drainage. 

 The absence of such a regulator causes disastrous floods. The regulator acts as a 

 sponge, and is supplied either in the form of a large area of forest, of swamps or 

 peat bogs, of a system of lakes, or of artificial reservoirs. Where there are no 

 forests, nature usually supplies their place with swampy moors. 



The surface of the wild moors where the springs of the Don and its tributaries 

 take their rise is covered with heath and ferns, and in winter, after heavy rains, 

 the ground is spongy, and persons have been lost and buried in it. A knowledge 

 of these moors explains the route taken by William the Conqueror in February 

 1070, in his winter march from York to Chester. The horses of the knights were 

 swallowed up by the treacherous swamps, and swept away by the torrents; 

 and the record of Ordericus Vitalis gives a vivid picture of a march across the 

 Penine chain in mid-winter 800 years ago. In this condition it long remained, 

 and even now the unchanging hills are little altered. But at the same time that 

 cultivation encroached on the moorland sponge, the necessities of great centres of 

 population have called for the construction of large artificial reservoirs, which also 

 serve the purpose of regulating the flow of surface drainage. 



There is the artificial lake of Dunford bridge near the main source of the Don. 

 The reservoir at Barker Pool, in use since 1434, appears to have been the first 

 artificial attempt to store water for use in Sheffield, and afterwards a chain of 

 dams in the valley on Crooks Moor met the demand. In 1864 the Dale Dyke or 

 Bradfield Reservoir was completed, covering an area of 78 acres ; and on the 

 11th of March it burst through the dam, making a breach 100 yards long and 70 

 deep. This appalling catastrophe, so admirably described by Mr. Harrison, shows 

 the irresistible power of floods in motion which, in other countries, are the work 

 of nature unaided by the labours of man. The cataclysms of the Indus, for 

 example, in 1841, and of the Sutlej, in 1819, were caused, not by faulty con- 

 struction of an engineer's dam, but by the rending away of the shoulder of a 

 mountain which had fallen into the river-beds. But the effects were similar. 

 The lesson of the desolating flood of 1864 was profited by in Sheffield, and the 

 work of storing water proceeded. In 1869 the Agden Dam was completed. The 

 Strines Reservoir was finished in 1872, the Dale Dyke in 1874, and the Dam 

 Flask in 1875, the united area forming, I understand, 300 acres of water. 



The necessity for the storage of water, owing to the destruction of forests, and 

 for irrigation purposes, is often a subject of discussion with reference to other 

 mountain ranges, and to disastrous floods in other countries ; and the native of 

 Sheffield may acquire a practical knowledge of many sides of an important problem 

 by an observant exploration of the hills and moorlands within a few miles of his 

 own home. 



The effects of human agency on the aspects of nature are also very strikingly 

 displayed in the country between Sheffield and Doncaster, and northwards towards 



