GEOLOGY. 259 



a depth of only thirty metres from the top. This accident it took 

 nearly three years to repair. A shaft of the depth of fifty-three and 

 a half metres had to be dug close to the bore, through all the most 

 dangerous strata, and lined partly with sheet and partly with cast iron 

 and masonry. Its diameter was three metres throughout the two- 

 thirds of its depth, and 1.70 for the rest. It was a work of extreme 

 difficulty. Cast-iron tubes, of the thickness of thirty-five millimetres 

 (four-fifths of an inch), were starred or cracked in all directions, as 

 if they were mere glass. More than once the workmen refused to 

 risk their lives in this work, and the city engineers had to set the ex- 

 ample of personal courage. 



This stupendous labor was not brought to an end before the thir- 

 teenth of December, 1859. The old orifice was then cleared, and the 

 boring recommenced, and continued without anv further accident to 



^J V 



the depth of 550 metres, when the tube, composed of wood strongly 

 hooped with iron, and ending in a bronze pipe, two metres of which 

 were fitted into the wood, the remaining twelve metres being free, 

 stuck fast in such a way as to render all further progress nearly hope- 

 less. However, M. Elie de Beaumont having, upon mature examin- 

 ation of the specimens brought up by the borer, declared water to be 

 close at hand, it was resolved that the bore should be continued with 

 a small diameter, to be afterwards enlarged, if necessary. Water 

 was found, for the first time, at 577^ metres, but, as we know, re- 

 mained a few metres below the level of the orifice. A second tube of 

 sheet iron, seventy centimetres in diameter, two in thickness, and 

 fifty-two metres in length, twelve of which were loopholed in order 

 to let the water pass, was sunk, and soon stopped in the clay. The 

 boring was now resumed, to attain the largest diameter, until the 

 twenty-fourth of September, 1861, when M. Kind saw not only his 

 promise fulfilled, but even his hopes to a certain extent realized. 

 The bronze tube has remained where it was, but the concentric one of 

 sheet iron has sunk to 380 metres. The yield of water from this well 

 is 20,000 cubic metres in twenty-four hours sufficient for the wants 

 of 500,000 inhabitants. At the same time the produce of the well at 

 Grenelle has diminished one-fourth. 



At the same meeting of the Academy, M. Gaudin presented a com- 

 munication in which he replies to the question, often asked, whether 

 the supply of the artesian wells, bored in the neighborhood of Paris, 

 can ever be exhausted. The stratum of green sandstone interposed 

 between the strata of chalk and Jurassic limestone is of the average 

 thickness of fifty metres; consequently, taking the depth of 577 

 metres of the artesian well at Passy as a criterion, there remains a 

 depth of twenty-five metres of sand. A cubic metre of sand, closely 

 rammed, weighs 1,600 kilogrammes, while compact quartz weighs 

 2,500 kilogrammes ; hence, the stratum of sand, even supposing it to 

 be closely packed, has interstices amounting to one-third of its bulk 

 in the aggregate, so that every cubic metre of sand under water con- 

 tains 333 litres of water. Now, the layer of sand existing under the 

 chalk may be represented by a disc of 160 kilometres' radius, its sur- 

 face amounting to 80,000 square millimetres, and its thickness to eight 

 metres. The cubic contents of this disc are, therefore, 640,000,000,- 

 000 metres, which, divided by 10,000,000, then by 365, gives the 



