18S0.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



193 



wells follow always an inverse ratio to the quantities of water ab- 

 stracted. Takinj; the Soho station at the end of February, when the 

 level was at the hifjhest, it will be seen that the average weekly 

 number of hours worked, for nine weeks equally distant from the 

 end of February, amounted to 70i, and the average quantity to 

 2,300,510 gallons, whereas in the following month of June, when 

 the level was lowest, the average number of hours jier week for 

 nine weeks amounted to ISflJ, and tlie average quantity to 

 4,160,881 gallons, a cause quite sufficient in itself to account for 

 the level of the water in the well subsiding without having 

 recourse to any more abstruse reasoning. At the ^Vater-street 

 station the average work for thirteen weeks, extending over March, 

 April, and May, was 65 hours per week, and the average quantity 

 pumped 2,552,095 gallons, while the average often weeks over part 

 of July, August, and September, was 8t hours per week, and the 

 average quantity pumped 3,084,129 gallons. 



These sections are, in my opinion, very informing when thus 

 accompanied by the weekly quantities pumped from the wells. 

 They show that, when the' draught is equal to tlie supply, the 

 general contour remains horizontal; that when tlie drauglit is 

 increased this line declines, and again becomes horizontal when 

 the equilibrium has re-established itself; and that the lower level 

 begins to ascend immediately the quantity abstracted becomes 

 reduced. It is therefore evident that the cause of the alterations 

 in level is chiefly to be ascribed to the abstraction of different 

 quantities of water by pumping. 



A careful study of the facts which have now been referred to 

 and explained has led me to the following conclusions: — 



That an abundance of water is stored up in the new red sand- 

 stone, and may be obtained by sinking shafts and driving tunnels 

 about the level of low water. 



That tlie sandstone is very pervious, admitting of deep wells 

 drawing their supply from distances exceeding one mile. 



That the permeability of the sandstone is occasionally interfered 

 with by faults or fissures filled with argillaceous matter, some- 

 times rendering them pai-tially or wholly water-tight. 



That neither by sinking, tunnelling or boring can the yield of 

 any well be very materially and permanently increased, except so 

 fur as the contributing area may be tliereby enlarged. 



That the contributing area to any given well is limited by the 

 amount of friction experienced by the movement of the water 

 through the fissures and pores of the sandstone. And 



That there is little or no probability of obtaining permanently 

 more than about 1,000,0U0 or 1,200,000 gallons a-day, and this 

 only when not interfered with by other deep wells. 

 (To be continued.J 



ON THE SEAVAGE OF TOWNS. 



At the last meeting of the Royal Agricultural Society of Eng- 

 land, Col. Grey informed the Council that this important subject 

 had, along with the general interest it had lately excited in the 

 piiblic mind, become a matter of interest and study to his Royal 

 Highness Prince Albert, and that lie was commanded by his Royal 

 Highness to bring before the Council of the Society, for their con- 

 sideration and inquiry, should they think the subject worthy of 

 it, what had struck his Royal Highness as being a simple plan for 

 effecting the object in view. Leaving it to more competent judges 

 to decide whether the sewage should be used as a liquid manure, 

 or solidified, upon which point his Royal Highness wished to give 

 no opinion himself, he had confined his consideration to the latter 

 mode of application, for two reasons, namely, that in the solid 

 form — 



1. It could be more easily transported; 



2. It could be obtained at the least possible expense. 



Colonel Grey then proceeded to describe the plan proposed by 

 his Royal Highness, which was simply this : — to form a tank, with 

 a perforated false bottom, upon whicli a filtering medium should 

 be laid; anlto admit at one end the sewage into the tank, bc/ow 

 the false bottom, when, according to the principle of water re- 

 gaining its own level, the sewage liquid would rise through the 

 liltering bed to its oi-iginal level in the tank, and provided tlie 

 filtering medium had been of the proper nature, and of sufficient 

 thickness, it would be thus freed from all mechanical impurity, 

 and would pass off into the drain, at the other end of the tank, as 

 clean and clear as spring water. Tliis simple and effective plan was 

 illustrated by drawings, sho« ing tlie \'ertical and horizontal sections 

 cf the tank, and by a neatly constructed modelof itsexternalforniand 



internal arrangements. It was also clearly shown by these sections, 

 how the sewage matter could be let into the tank, or shut off, when 

 necessary, in the simplest manner, by means of common valves; 

 and with what facility such a filtering tank might be applied to 

 every existing arrangement of sewers without requiring any altera- 

 tion 'in their structure. The filtering medium having abstracted 

 from the sewage all extraneous matter, would, in all probability, 

 become the richest manure, and could, at any time, by stopping 

 the supply of sewage, be taken out by a common labourer with a 

 shovel, and carted or shipped to any place thought most desirable. 

 The solid matter, too, field in suspension liy the sewage, would 

 probably form a very rich deposit at the bottom of the tank, of a 

 substance approaching in its qualities to guano, and could be 

 extracted by removing tlie false bottom, which rested on arches or 

 vertical supporters over the sewage beloiv it in the tank, and could 

 be easily made to lift up or take out for the purpose of such extrac- 

 tion. Two tanks might easily be constructed together, so that one 

 might continue in operation while tlie other was being emptied. 

 Tlie experiment niiglit be tried at any house-drain in town or 

 country; in fact, his Royal Highness liad himself tried the opera- 

 tion on a small scale with apparent success; and while he thus 

 suggested an important and extensive application of the hydrosta- 

 tical principle involved in the plan proposed, he wished to lay no 

 claim to originality in the adoption of that well-known law of fluid 

 bodies by which they make an effort, proportionate to their dis- 

 placement, to regain'their original equilibrium. On that principle 

 was founded as he was well aware, the upward-filtering apparatus 

 used by the Thames water companies. His Royal Highness's great 

 object was by the simplest possible means to attain a great end; to 

 effect an essential sanitary improvement, and at the same time to 

 create a new source of national wealth by the very means employed 

 for the removal of a deadly nuisance, and the convei'sion of decom- 

 posing matter highly noxious to animal life into the most powerful 

 nutriment for vegetation. 



His Royal Highness, too, wished to offer no opinion on the 

 details required to complete the plan proposed, or on the mode of 

 carrying it out in the most effective manner. Supposing it to be 

 right in principle, its advantages in an economical point of view 

 could only, his Royal Highness conceived, be ascertained by prac- 

 tical experience; and it was on that account that he wished to sub- 

 mit it to the consideration of the Agricultural Society, who might 

 be better able to carry out the necessary experiments. It would 

 remain to be decided what is chemically or mechanically the best 

 and what the cheapest substance for the filter; what the best and 

 cheapest construction of the tank; how long the sewage will pass 

 before the filter becomes choked; and how soon the filter could be 

 sufficiently saturated to make it profitable as a manure. His Royal 

 Highness had used as the filtering medium, the following sub- 

 stances: — 



1. Charcoal: — admitted to be the most perfect filtering substance 

 for drinking water, retaining effectually extraneous matters, and 

 well known for its singular powers of purification. 2. Gypsum 

 (plaster of Paris, or sulphate of lime): — recommended by agricul- 

 tural chemists for fixing ammonia and other volatile substances, 

 by the decomposition to which it becomes subject when exposed to 

 the action of volatile alkali. 3. Clay: — in its burnt state, would 

 act mechanically as a filtering bed ; and in its unburnt state, on 

 account of its aluminous salts, has also the property, like gypsum, 

 of fixing ammonia, or of decomposing the ammoniacal and otlier 

 alkaline salts present in manure: and in either state would be 

 cheaply procured. 



All these substances, his Royal Highness thought, would in 

 themselves be highly useful as manures, independently of the 

 purpose they would subserve as agents for filtration, or for the 

 additional amount of manuring matter they would receive from 

 the sewage which they purified. His Royal Highness, however, 

 in thus incidentally referring to the substances he had himself 

 employed for the filtering medium, was well aware how many more 

 of equal, if not superior, value, would suggest themselves to others, 

 who, like himself, felt an interest in effecting the important object 

 proposed. As he had given no opinion on the general question of 

 liquid or solid application of manure, but had merely stated the 

 grounds of preference, in a practical sense, of the solid form over 

 the liquid for the purposes of the filtering operation under con- 

 sideration, his Royal Highness entered into no discussion of tlie 

 amount of maiuirii'ig matter retained by the filter compared with 

 the soluble matter that might pass through it along with the water, 

 and remain in that liquid in a soluble, colourless, and transparent 

 form; nor of the value of such filtered water for agricultural 

 purposes. 



27 



