xx. WATER SUPPLY. 499 



by painters simply of itself, and as often mixed with the rest 

 of their colours.' It is still good of its kind, but the demand is 

 not such as to maintain its former commercial value. Associated 

 with the ochre are some argillaceous bands which are of the nature 

 of fuller's-earth, and white and yellow sands. The white sands 

 in the hill above Hartwell have been used with success in glass- 

 making. Tobacco-pipes were made commonly during the siege of 

 Oxford from a bed of white clay which lies above the ochre of 

 Shotover ; and the substance was of use to statuaries for making 

 ' models, gargills or anticks,' and polishing silver, so says Dr. Plot. 

 Fuller's-earth was formerly dug in the Vale of the Cerne to 

 supply the wants of the clothiers of Gloucestershire, but modern 

 chemistry has driven the natural product out of its only market. 



WATER. 



Water composes half the weight of the food which we call solid ; 

 we add for drink as much in weight as that food : how essential, 

 then, to our pleasure, comfort, and health that the element should 

 be wholesome. It seems not necessary, perhaps it may not be 

 desirable, that the water we drink should contain no salts of lime, 

 or magnesia, or iron, or soda ; but it must not have these in large 

 proportion unless employed medicinally. Carbonic acid is pleasant, 

 and perhaps useful ; but organic impurity, even in small quantity, 

 is extremely injurious, and acts as a poison. 



To stand by the rocky cradle of a great river 



'Ad aquae lene caput sacrse,' 



and consider the eventful course of the life of the new-born 

 stream ; to see it burst exulting from leafy shades into freer air, 

 and follow it sweeping into larger valleys and broader plains, 

 is at once delightful and instructive. Yet not more pleasing or 

 instructive to contemplate the full outrush of the young Danube, 

 than to look upward and downward from Trewsmead along the 

 solitary valley in which no drop of water is usually seen at the 

 traditional fountains of the Thames. 



Here in former days the Roman legionaries halted to slake their 

 thirst at the perennial stream which had been for long ages before 

 the resource of the shepherds and warriors of the Dobuni and earlier 

 races ; and it has been reserved to our own days to extinguish 



K k 2 



