246 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[July, 



formed at the buck of the brick shaft about tiO feet from tlie surface. 

 The settlement of the ground at the surface was so extensive that tlie 

 pumping the works was discontinued until the phxn suggested by Mr. 

 Simpson, of continuing the sinking with the water in tlie well, was 

 adopted. 



For this purpose, in August, 1836, a wrought iron cylinder of boiler 

 plates, 62 feet long, and 5 feet 10 inches diameter, was lowered to the 

 surface of the sand, which was hard under the ))ressure of the water, 

 and removed by an instrument called a miser, and which holds about 

 two bushels. The cylinder was forced down by hand screws on its 

 upper edge, through tlie remainder of the (juick sand stratum, through 

 a bed of sand with flints and pebbles, and through a bed of chalk and 

 flints, into the chalk to a depth of 12 inches. The water and sand 

 being now shut out, the well was dried, and in March, 1837, the sink- 

 ing continued in the usual manner to a total depth of 183 feet, the 

 chalk being sufficiently indurated to require no lining. The water now 

 increasetl considerably, and the chalk was excavated to an enlarged 

 diameter below the bottom of the wrought-iron cylinder, for the pur- 

 pose of forming a brick footing. On the top of this is a broad cast- 

 iron ring, upon which rest cast-iron cylinders of a clear diameter of 4 

 feet 7 inches, which were introduced within the wrought-iron tube, 

 for the purpose of strengthening and guarding against the admission 

 of sand in case of its failure from corrosion. 



In February, 1838, the works being complete, the pumps of 12 inch 

 diameter were introduced in two lifts; and in August, 1S38, when the 

 springs were short, and in March, 1839, when the springs are at their 

 best, an experiment of two weeks was made ; the result of the former 

 was 14,898, and of the latter, 30,499 cubic feet per day of 24 hours. 

 The total expense of the well was 12,4 12/. 14s. \d. 



The paper is accompanied by a copy of the report of James Simp- 

 son, Escj., in which the plan adoj)ted for tlie completion of the works 

 is recommended. Mr. Simpson details the difficulties which had been 

 met with, and particidarly the extensive subsidence of earth caused 

 by the removal of the sand. This far exceeded the quantity due to 

 the contents of the well at the lower sand stratum, and the subsidence 

 proceeded most rapidly when the water was pumped out of the well. 

 The experience of wells near the metropolis shews that the springs in 

 the chalk are much more abundant than in the sand, but in order pro- 

 perly to avail ourselves of these there nmst be adits driven to unite 

 the water from the fissures in the cavernous structure of the chalk. 

 The report proceeds to speak of certain methods of securing the pre- 

 sent works, and of prosecuting them by either driving an iron pile curb 

 or sinking iron cylinders cast in entire circles. The former cannot be 

 recommended, as a considerable further subsidence would be the con- 

 sequence, and the shaking of the ram would endanger the works. The 

 latter is performed with common boring rods and tools, the shells or 

 buckets are fitted with valves opening upwards, and the material is 

 raised by them with the greatest ease. When the cylinders be- 

 come set, or when they do not sink in proportion to the material 

 removed, they are slightly jarred by a heavy sledge hammer. The 

 advantage of keeping the "water in equilibrium inside and outside the 

 cylinders is very great, and the method has Ijeen found in many cases 

 most efficacious. 



The paper is accompanied by a section of the works and the strata, 

 and by drawings of the various tools employed. 



Mr. Brunei stated, that the succession of the strata here described 

 was nearly the same as they had met with at the Tumiel. 



Mr. Simpson remarked, that the greatest caution was requisite in 

 drawing conclusions respecting the strata in one part of the metropolis 

 from wTiat was known of it in another part. At Lambeth, for instance, 

 in the same shaft, there might be gravel on one side and sand on the 

 other, and the London clay here is about 32 feet below Trinity high- 

 water mark : near Chelsea College the London clay is met at the depth 

 of 38 feet, after passing through sand and gravel, and a little farther 

 on, in the King's Road, the clay is reached without passing through 

 any sand, and in this locality the chalk is touched at 245 feet below 

 Trinity high-water mark. It was a remarkable fact that they sliould 

 have reached chalk at so small a depth in the Tottenham Court Road 

 well. The alterations in the strata are so great, tliat no one who has 

 had any experience of wells will venture to infer from one place what 

 will occur at another. The engine employed at this well w as a twenty 

 horse, and worked at an expense of about 21. 7s. per 24 hours. This, 

 however, is a very small part of the expense of supplying water to 

 houses, as the water has to be raised to the liouses, and tlie cost of 

 pipes must be included. It was not very intelligible liow water is to 

 be raised from so many feet from below high-water mark, and supplied 

 at the same cost as water taken from the Thames at the level of high 

 water. 



SECTION OF THE WELL AT THE HAMPSTEAD ROAD. 



Blue Clay. 



Coloured Clay. 



Sand. 



r^*^-xx^r^"::^^'',-^ Le\'el of Water. 

 -^^.-Jo -Y ,v"<j>,-\.i Coloured Clay. 



-•^ !r.:s» - ..^^ e^Cj '- Sand with Pebbles, 

 lard Sand. 

 Sand with Flints. 



— ■ I ^ 



k^-,^..^-^t>L Runnin 



unnmy fcanu. 



■^,^^Aa FlinlB. 



