328 WATER-BEAKIXG STRATA. 



structed to depths of from 1,500 to 3,000 feet, of five and 

 six inches diameter. 



These are formed by using a " trepan," or '' bit," through 

 a wooden tube sunk into the surface of the ground for a 

 few feet, through which the trepan (fastened at one end of 

 a lever to a cord of ratan), weighing three or four cwt., was 

 worked, a man at the other end of lever raising and de- 

 pressing it, and so jumping the hole through the strata, a 

 circular movement being given to cause it to take a different 

 turn at each drop by a cross arm of wood. These are said 

 to have cost a " tael " a foot ; a '' tael " is equal to 6s. 3d. 



In France the art of boring was early known, notably in 

 the province of Artois, from whence the well-known term of 

 Artesian well boring takes its name. One of the earliest of 

 these wells was executed at Lillers, in the Artois, in 1126. 



In our own country the first recorded instance of boring 

 by this method is when Sir C. Wren adopted it to ascertain 

 the nature of the strata under the foundation of St. Paul's ; 

 and in the latter part of the 18th century such borings were 

 made in Great Britain in the wolds near Louth in Lincoln- 

 shire, and in the London basin near Tottenham. 



To leave original practice, and turn to that of our own 

 day, I will confine myself to wells and borings in the Chalk 

 and New Red Sandstone, with which I am more familiar, 

 although there are other measures where water is abun- 

 dantly found ; for instance, in the Pennant Grit between the 

 Upper and Lower Coal-measures, the Millstone Grit and 

 Old Red Sandstone. 



Before going on to the actual description of the work of 

 sinking and boring, it would be well to glance at the par- 

 ticulars of the rainfall, the source of the water suj^ply, not 

 only of wells, but of rivers, and brooks, and surface springs. 



The average rainfall of England and Wales has been 



