334 On Wells used in Foundations in tipper India. ^April, 



these notes are especially addressed) ; the piers of the Hindun bridge 

 resting on wells up to the limit of the table above proposed. 



It must be recollected that the cylinders are supposed to be under- 

 sunk from the commencement through a sandy soil, and with spring 

 water at the surface — as must usually occur in foundations where the 

 application of them for that purpose would be necessary. The cost of 

 village wells, which although thirty or forty feet deep are only under- 

 sunk on reaching the springs, is proportionably less. 



With reference to the value of obtaining a connected curtain, or line 

 of running wall in foundation, where the interference of spring water 

 renders undersinking necessary, Colonel Colvin, C. B. of the Bengal 

 Engineers, proposed a plan of sinking square masses or parallelopipe- 

 dons of masonry, piercing these masses by wells, as represented in Fig. 

 1. PI. 3. The plan succeeded in every respect. In those of from ten to 

 fifteen feet long and four feet wide, undersinking to a depth of ten feet 

 in sand mixed with small shingle was carried into execution with 

 perfect success in the foundations of the dam over the Somhe river. 

 Water was, at the point where the dam had to be constructed, immedi- 

 ately on the surface ; the object of the dam was to retain the supply of 

 water to a considerable height to throw it into the Delhi Canal, and 

 maintain a supply during the dry months. Circular wells were objec- 

 tionable for the reasons which I have before explained, and it was a 

 desideratum to get such a foundation, that the head pressure of water 

 should affect the leakage under the dam as little as possible. Fig. 

 1. PI. 3. will explain the method adopted, the spaces between the 

 boxes on the first row being covered by those in the second line. 



The method put into practice in sinking these masses is similar to 

 that in cylinders, but greater care is required in regulating the opera- 

 tion of the well-sinkers, so that the mass may be lowered equally. The 

 curb, or neemchuk, is a platform of wood equal in size to the base of 

 the masonry, with round or oval holes cut for the wells, as shewn 

 in Fig. 1. PI. 3. I have used these masses in lengths of twenty-one, 

 feet, by four feet wide, to a depth of ten feet, with perfect success, 

 giving three wells in each. I should however limit the dimensions to 

 fifteen feet by four feet, with two wells elliptical, five feet by two and a 

 half each, which with proper care will be sunk to a depth of ten feet 

 through sand without any difficulty. There appears no reason why 

 a whole foundation of a work within certain limits might not be sunk 

 in this way. It is often a difficult matter to obtain foundation for a 

 bridge with an arch of twenty feet span where the soil is sand 

 although the drainage is not liable to freshes or any violence of cur- 

 rent. A bridge of this sort, with a roadway of fifteen feet, would 



