1844.] 



THE CIVIL ENGINEER AND ARCHITECrS JOURNAL. 



281 



so impottanl a subject. L'o tliis eiul wa aic amtimiiny our unvciiiitting ex 



We purpose giving the Engineering evidence referred to in the report, 

 which we shall slightly abridge, and in order to avoid giving both question 

 and answer, we have condensed the two into one. 



On the Supply ok Water to Towns. 



Mr. Robert Thorn. — He has paid attention to the mechanical means of 

 supplying towns with water for about 30 years. The towns of Greenock, 

 Paisley, and Ayr have been supplied with water on his plans and superin- 

 tendence. Plans and estimates for the supply of other towns, and of many 

 other places, have been given by him, but the duties of his business of cotton 

 spinning rendered it impossible for him to superintend the details of execu- 

 tion, except in the case of the Rothesay Spinning Mills, the first of his hy- 

 draulic operations on a large scale. 



Mr. Thom explained to the Commissioners the principle of his plan, as 

 distinguished from other modes of supplying towns, as follows : He imagined 

 that, in answer to their question, it was enough to describe generally his own 

 plan. The distinguishing features of which were, the obtaining some 

 natural basin at a sufficient height, either in itself containing a large supply 

 of water, or into which a great extent of surrounding surface can be drained. 

 Thus a reservoir is formed, which he takes care shall be deep enough to main- 

 tain the water at a low temperature, and to prevent the breeding of insects and 

 the growth of vegetables ; and capacious enough to hold at least four months' 

 supply of water. If it be not possible to obtain a large enough extent of 

 drainage surface at one place, other basins are sought for and form auxiliary 

 reservoirs, the waters of which are conducted into the main reservoir by 

 aqueducts furnished with sluices of a pecularly simple contrivance. To facili- 

 tate the collecting of the water from the surfaces, catch water drains are 

 made use of, and advantage, of course, is taken of any rivulet, spring, or 

 collection of water which may he accessible. From the main reservoir the 

 water is led by an aqueduct to some place near the town, where reservoirs 

 can be formed, at such a height that the water from them will rise consider- 

 ably above the highest houses. There, two reservoirs, or as I term them, 

 regulating basins, are formed, each of them large enough to contain two days' 

 supply of water. From these regulating basins the water is carried into two 

 or more self-cleaning filters, and from the filters into two distributing basins ; 

 the regulating basins, filters, and distributing basins being in juxta-position, 

 and so arranged that one of each of them may be connected together to form 

 a set of apparatus. Two sets of apparatus are required, that the one may be 

 in use while the other is cleaning or repairing. From the distributing basins 

 the water is carried through the streets by supply of pipes of iron, placed iu 

 such a manner as that the water shall always flow in one direction, entering 

 at the higher and wider end and flowing to the lower end ; and always kept 

 full of the water at high pressure, so that there may be a supply in readiness 

 for every emergency. These are the principal features of his plan, but its 

 efficiency depends so much on a host of minor details, that he has thought it 

 right, iu the subjoined note, to describe these more fully. It may be observed 

 here, however, that although there is nothing remarkable in collecting sur- 

 face water to fill reservoirs, and in carrying it from these by aqueducts, pipes, 

 &c., for the supply of towns, yet there may be, and often are, in the modes 

 of forming these reservoirs and aqueducts, and in the contrivances to ensure 

 their permanent working condition, such difference as that while the expense 

 of one method shall form a perfect bar to its adoption, another mode shall 

 recommend itself by its simpHcity and economy, and it has been his con- 

 stant endeavour to unite simplicity and strength, so as to ensure pervianent 

 durability and prevent y«/Mre expense. 



In a letter Mr. Thom stated, "In every case where the distributary basin 

 can be placed high enough, the pipes in the streets ought to be kept con- 

 stantly full, so as to be always ready at a moment's notice to extinguish 

 fires ; and the distributary basin should be placed high enough to send the 

 water over the tops of the highest houses, by merely putting the hose of a 

 fire-engine on one of the fire-plugs, which should be attached to the pipes at 

 short distances through all the streets. This I have done in Greenock, Pais- 

 ley, and wherever I gave the plans ; the advantage is immense ; and were it 

 properly and generally practised, there would be little need for insurances 

 from fire. Provision should also be made for cleaning the streets, lanes, 

 sewers, &c. by the water. When the cholera commenced at Greenock, the 

 many dirty streets and lanes in that town were cleansed by a copious supply 

 of water sent down from the Shaw's Water Aqueduct. Hence, in all proba- 

 bily, the few deaths which hap])ened there, compared fo those at Dundee, 

 Dumfries, Musselburgh, and other places similarly low and dirty." Mr. 

 Thom is of opinion that that which was done at Greenock would serve other 

 towns, wherever there is head pressure enough to raise the water over the 

 houses, whether that pressure is obtained by gravity or any power. By the 



gravitating system no additional expense is incurred ; but where steam or any 

 other power is used to raise the water the expense is very great. Hence the 

 unwillingness of water companies, who have to maintain a mechanical power 

 to keep their pipes full at high-pressure. 



It is stated that in the city of Philadelphia a similar arrangement has been 

 adopted of keeping the water always on at high pressure ; and that for the 

 cleansing of the streets a servant girl will put on the hose in the morning, 

 and with this hose sweep the pavement, that once a week a stronger hose is 

 used, and they sweep or cleanse the front of the house up to the highest win- 

 dows ; and that, on an occasion of fire, they immediately apply the hose, and 

 introduce it into the interior of the house, and into the room where the fire 

 takes place ; is that an arrangement which you believe, from your experience 

 at Greenock, is generally practicable ? — It is perfectly practicable, under the 

 conditions noticed in my answer to the foregoing query. It was practised by 

 myself on a small scale 30 years ago. 



With respect to the modes of laying the water-pipes for distribution, are 

 there any defects common, which you think you have avoided in places where 

 you have had occasion to superintend the supplies of water ? One common 

 defect is the permitting the water to flow along the pipes in either direction 

 occasionally, thus stirring up the sediment, and sending a stream of turbid 

 water into the bouses. 



Is that error in distribution a fault which might be prevented in very large 

 supplies, or only in small towns ? — It may be prevented in all supplies, whe- 

 ther for large or small towns, if proper arrangements be made at first. 



With respect to the filtration of water, have you adopted any peculiar 

 modes of filtration, to which you can speak as having been successful in any 

 places where you had the superintendence of the supply .' — At Greenock, 

 Paisley, and Ayr, I erected self -cleaning filters.^ 



The cost of this filter was under 600/., and the quantity of pure water pro- 

 duced regularly every 24 hours is, on the average, 106,632 cubic feet. The 

 expense of a filter, therefore, to give a supply of water of the best quaUty/oc 

 family purposes, to a town of 50,000 inhabitants, may he safely taken at 

 800/. From often finding pure spring-water in the moors, where the soil for 

 many miles was composed of peat or moss, I suspected there was some sub- 

 stance in the earth which, by combining with the tannin or colouring mat- 

 ter, rendered the water pure, and this was proved to my entire satisfaction by 

 a careful' inspection of the minerals in the hills above Greenock. I there 

 ascertained that the moss water, by flowing over or through a particular species 

 of lava or trap-rock (amalgoiloid), became fine spring water. Since then, I 

 hEve used the substance as a substitute for charcoal, with perfect success and 

 much economy. A very large proportion of the hills above Greenock being 

 composed of this substance, it may be had at a nominal price. 



The filters are composed of very fine pure sand, mixed with animal char- 

 coal for the purpose of decomposing any vegetable matter with which the 

 water may be impregnated. The effect of such a filter, besides decomposing 

 vegetable matter, is to render the water clear though previously turbid. 

 Animal charcoal is the most powerful agent he knows of. He has contrasted 

 its action with that of ordinary charcoal or a mixture of ordinary charcoal 

 with other substances, and found it more powerful and to last longer than 

 ordinary charcoal. — He has used ordinary charcoal with other substances ; 

 but finding that it lost its effect sooner than animai charcoal, he discontinued 

 its use. — Some kinds will last several years. The sand did not contain any 

 other earthy substances ; it was clean from the sea-shore, of a lightish brown 

 colour. The filter only had one stratum of coarse sand, the under part of which 

 is gravel, next a fine gravel, and so on finer and finer to the depth of six or 

 seven inches — and after that the fine sand above mentioned. He mixed the 

 charcoal with the sand. — He has a small head of water of only one or two 

 feet at most upon the filter ; the purest water is produced with a small 

 pressure. — A filter of 0000 feet area supplies a population appro.ximating to 

 40,000 people ; but it depends much on the previous purity of the water. 

 It would be -within bounds by taking half the proportion for a filter of that 

 size. — He has no precise data as to the quantity of animal charcaal required 

 for a given quantity of water. He uses the charcoal in about the proportion 

 of one of charcoal to eight or ten of sand. The same charcoal might be used 

 over again, after subjecting it to the purifying process, if it could be sepa- 

 rated from the sand. He has not the power of separating it from the sand 

 when it is used in the proportion stated ; and, indeed, it would not be worth 

 while, as the quantitity is so small and lasts so long. I have sometimes used 

 charcoal in large layers by itself, and in such cases it might, with economy, 

 be reburned and used again. 



In a letter Mr. Thom has stated, " Where rivulets or lakes are not in the 

 vicinity, the surface-water alone might, in most cases, be rendered sufficient, 

 if artfully and economically diverted into reservoirs by small aqueducts, as at 

 Rothesay Mills. The average annual depth of rain which falls in Great 

 Britain is probably above three feet ; in the west of Scotland it is greatly 

 more ; and at Paisley and at Greenock Waterworks, I have ascertained that 

 about eight-tenths of the whole has been made available to tlie reservoirs. 

 At Rothesay, where the declivity of the ground is less, and its surface more 

 broken and porous, the proportion available is only about six-tenths of what 

 falls there. 



He considers that, by proper economy, the surface water in the vicinity of 

 towns and places m.iy be made available to a greater extent than is commonly 

 supposed. 



He had already stated that, in some cases, eight-tenths, and others only 



Wc shall give a drawing and deacription of the filter ne.\t month,— Kditor. 



