4i8 



SCIENTIFIC NEWS. 



[May 4, iS 



THE CITY ARTESIAN WELL BORING. 



HTHE artesian well that the City Commissioners of 

 Sewers are sinking for the supply of their artisan 

 dwellingsjust off Houndsditch is making slow, but steady, 

 and on the whole, satisfactory progress. The special 

 interest attaching to this work arises from the fact that 

 if it should be found practicable it is the intention of 

 the Commissioners to provide a supply of water not only 

 for the thousand people for whom they have set up 

 model dwelling accommodation, but for various public 

 purposes within the City. That enough will be reached 

 for the supply of the fine blocks of dwellings recently 

 erected by the Corporation there can be no reasonable 

 doubt, since, as a matter of fact, wells have already been 

 sunk in various parts of the City, and have yielded 

 splendid water in quantities quite sufficient for the 

 Commissioners' immediate purpose. But we believe it 

 is an admitted fact that the level of the water in the 

 chalk under London has steadily been going down for 

 many years past ; and if anything is to be done for the 

 benefit of the City at large it may be that Colonel Hay- 

 wood will have to seek a supply deep down beneath the 

 chalk. 



The level of the ground on which the boring has been 

 undertaken is about that of the roadway in Houndsditch 

 and the neighbourhood generally; nevertheless, about 

 ten feet of made soil — " shot rubbish " — had first 

 to be gone through, and at a depth of something more 

 than this was found a halfpenny of the year 1862. Some 

 old cellar excavation might possibly account for this, but 

 fragments of Roman tiles, very old crockeryware, and 

 clay pipes of the pattern in which they were made 

 probably at the time of King James's famous " counter- 

 blast," dug up at depths of from eleven to fifteen feet, 

 afford interesting evidence of the gradual rise of surface 

 level at this spot, and since, as it has been said, the 

 surface here is just about that of the surrounding neigh- 

 bourhood, it shows that the ground on which London 

 stands is now many feet higher than it was generations 

 ago. This fact alone would no doubt be sufficient to 

 account for very important changes in the health of the 

 metropolis of the presentday as compared with what it was 

 in the past. The river level of the gravel under London is 

 about seventeen feet eight inches below the existing 

 surface. The well seems to have struck into a dip or 

 pocket in the surface, and in this hollow a human skull 

 was found embedded — washed into it probably long ages 

 ago, when the site of Houndsditch and Bishopsgate and 

 busy Whitechapel was a desolute marshy waste, subject 

 to alluvial action. 



Water was touched at 11 ft. 3 in. above Trinity high 

 water mark, and an important part of this undertaking 

 is the stopping out of this surface water. In order to 

 effect this, as the excavation proceeded through the Wool- 

 wich and Reading series, huge iron cylinders with an 

 internal diameter of 9 ft. 6 in., and each weighing about 

 four tons, were lowered one on the top of the other, so 

 that the low/er ones were driven down by the sheer 

 weight of those above as the digging down below pro- 

 ceeded. There are seven of these great sections of tube 

 now in the well, and these being tightly bolted together 

 form a barrier quite impervious to surface water. The 

 excavation is now going on through the London clay, 

 and here the wall of the well is being constructed of brick, 

 the bricklaying having, of course, to be carried on down- 

 wards. When the excavation has got clear of the clay. 



cylinders will be employed through the Thanet sands 

 and for some distance into the chalk. The present work 

 will terminate with a boring of 100 feet in the chalk. 

 The geological strata underlying London seem to be 

 involved in some obscurity, and it is well known that 

 leading geologists have made one or two serious mistakes 

 in connection with this matter of well boring. Should 

 the Corporation succeed in tapping a copious flow of 

 water it may lead to further experiments of the kind and 

 to the serious discussion of ways and means of utilising 

 the supply. 



ABSORBENT QUALITIES OF CHARCOAL. 



MOST people know that charcoal is largely 

 employed for purposes of filtration, but only 

 a comparative few understand why. From its 

 porosity this material is one of the most powerful 

 absorbents we possess, and, from this property and 

 the ease with which it can be prepared, is of great value 

 both for the absorption of gaseous as well as liquid pro- 

 ducts of decomposition. The charcoal employed is 

 generally of two kinds, vegetable or animal. The first 

 may be prepared either by the partial combustion of 

 wood in the old rough-and-ready fashion by arranging it 

 in heaps covered with turf and sand, or by the more 

 scientific method of distilling the wood in closed vessels 

 or retorts, whereby the products of distillation, such 

 as wood, tar,water, naphtha, etc., are obtained, as well as 

 the porous charcoal. Animal charcoal is obtained from 

 the partial combustion of bones, and differs from vege- 

 table charcoal in containing a much larger quantity of 

 mineral matter. The absorption of gases by charcoal 

 varies according to the nature of the material from 

 which it is prepared, wood of great density, such as box 

 or cocoanut, generally yielding the most absorptive 

 variety of charcoal. This absorption has been examined 

 by De Saussure, Angus Smith, and Hunter, and the co- 

 efficients of absorption for certain gases are as follows : 

 — One volume of charcoal absorbs 90 volumes of am- 

 monia gas, 85 of hydrochloric acid gas, 65 of sulphur 

 dioxide gas, 55 of hydric sulphide gas, 40 of nitrous 

 oxide gas, 35 of carbon dioxide gas, 9-4 of carbon, mon- 

 oxide gas, 9-2 of oxygen gas, 6-5 of nitrogen gas, and 

 l'25 of hydrogen gas. The more readily a gas under- 

 goes liquefaction so does its absorption by charcoal in- 

 crease, such gases as oxygen, hydrogen, and nitrogen, 

 which are not easily reduced, having a very small co- 

 efficient of absorption. But some gases are not only 

 absorbed by the charcoal, they also undergo a certain 

 amount of decomposition from the air already held in 

 the pores of that material. This is seen to be very 

 markedly the case with such gases as hydric sulphide, or 

 with those derived from the putrefaction of material rich 

 in nitrogen. In the former case the gas becomes con- 

 verted into sulphur dioxide in a manner analogous to its 

 decomposition during incomplete combustion. After a 

 time the sulphur dioxide undergoes oxidation in the pre- 

 sence of moisture, resulting in the formation of sulphuric 

 acid. Free sulphur can also be extracted from the char- 

 coal by the proper solvents at a certain stage of the ab- 

 sorption. 



••->t^^5tf-» 



Shower of Ashes. — On January 5th a shower of 

 ashes fell at Elverum, in central Norway. It is supposed 

 due to a severe volcanic outburst in Iceland, intelligence 

 of which has not arrived. 



