26 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL 



[Jan. 



ucers, 1 intioiluced a clamp to he used by signal Tilien the cross hair of the 

 instrument has been brought nearly to coincide with the centre of the vane, 

 leaving the rest of the adjustment to be made with the screws, liy this ar- 

 ranecment the great loss of time arising from the rough process of adjusting 

 the Vane by the hand is completely obviated, and the sliding vane rod, which 

 is certainly the best instrument where great nicety is required, is thus freed 

 from these objections. This iiistrun)ent is tiierefore adapted to the most 

 accurate purposes, always, excepting indceil researches such as those of Mr. 

 Bunt, who read i ff to /our places of decimals, while at the same time the 

 self-reading graduation on the back of it renders it equally well adapted for 

 every operation connected with engineering, and there is no reason, as Mr. 

 Townscnd seems to imply, why the readiiigs should be pushed to a greater 

 degree of accuracy than the wants of the observer, or the delicacy of his in- 

 strument may warrant. 



^Vith legard to the spherical or circular level which Mr. Townsend seems, 

 so far as I can understand, to employ in a somewhat ditferent way to me, I 

 have to mention that n;y communication on that subject to the Institution 

 is dated the 30th of January, 1841, although it was not read till tlic 4 th of ilay. 

 The great superiority of the spherical level as used by me consists in the 

 tlii/ness of its mo/ion, a quality rendering it peculiarly fitted for the pur)>ose 

 assigned to it. 



Mr. Townsend takes exception at the ball and socket joint, but I would 

 oljserve that the surface of the ball which is in contact with the clamping 

 zone is very considerable, aiul the friction produced so great that no un- 

 steadiness is found to be produced by this construction in instruments for 

 ordinary purposes. In such an instrument as a single second-level, which is 

 only to be used for extraordinary purposes, I would not [)ropose to adopt the 

 ball and socket, as any metliod for saving time in setting such an instrument 

 is of no value. In such a question as this, experience is erer;//hinff, and I 

 have to state that having now used that instrument on some 40 or 50 diffe- 

 rent occasions, I cannot forget the great facilities it has afforded, and the 

 time it has saved me, more especially when a rising tide rendered time of 

 paramount importance. I firmly believe that any one offer a dni/s experi- 

 ence of it, would admit it to be the most desirable instrument he had ever 

 used. 



I remain, your obedient servant, 



Thomas Stevenson. 



Edinlurgh, Dec. 10, 1841. 



P.S. I do not consider it necessary to occupy valuable room in noticing 

 the observations of Mr. Bewlev. 



PROCEEDINGS OP SCIENTIFIC SOCISTIES. 



INSTITUTION OF CIVIL ENGINEERS. 



June 29. — Henry Robinson P.vlmer, V. P. in the Chair. 



The following were elected : — George Briant Wheeler Jackson, as a 

 Graduate; William Crellin Pickersgill, William Millar, Robert Cantwell, 

 Thomas Clark, and Hugh Roland Laljatt, as Associates. 



" Description of the Bann ResoToirs, Cortnty Down, Ireland." By John 

 Frederick IJateman, M. Inst. C. E. 



The construction of the reservoirs described in this communication was 

 undertaken with the view of regulating the quantity of water in the River 

 Bann, and more effectually supplying water power to the flourishing and in- 

 creasing estabhshments on ils harks; this liver is, from the bare and naked 

 character of the Moume Mountai , among whicli it rises, naturally liable to 

 the greatest irregularity in its •\ uiiuue ; devastating floods frequently pour 

 down the channel, where a few hours previously there was not sufficient 

 water for agricultural purposes : greatly injurious as this must have been to 

 the agriculturalist, it was infinitely more so to the mill-owners, who depended 

 entirely upon water power for their manufactories. 



Mr. Fairbairn was consulted on the subject; he examined the locality, and 

 advised the formation of reservoirs : the author was then appointed the engi- 

 neer, and a' ting in some dt^grec upon the suggestions of his predecessor, 

 whom he continued toiconsult, the works were undertaken which are described 

 in the present paper. 



The peculiarities in the act of parliament, granted in 1836, constituting the 

 proprietors of the mills a Joint Stock Company, for the formation of the 

 Bann reservoirs, are detailed. 



The works were originally intended to have been more extensive than have 

 beenically executeil. The reservoir at Lough Island Heavy, is alone described : 

 the groinid in tliat spot was admirably adapted for the work, being the bot- 

 tom of a basin, which was bounded on all sides by rugged hills of granite ; 

 in the centre of the basin was a stnall lake, at the bottom of which was dis- 

 covered a bed several feet ip thickness, of fossil conferva;, similar to those 

 discovered by Professor Silliiwan at Massachusetts, North America. This in- 

 teresting geological Act was tirst notic&d by Dr. Hunter, of Bryansford ; the 

 conferv.T appeared like an ijuijalpabfc powiler, but when viewed through a 

 powcrfid microscope, they w ere fouml to be regular parallelograms, many of 



them covered with stritc. They are described by naturalists as the fossil 

 skeletons of minute vegetables. 



The situation fixed upon for the reservoir, rendered necessary the con- 

 struction of four embankments between the hills, so as to raise the water to 

 a height of .35 feet above the summer level of the lake. 



These embankments were all constructed in a similar nianner, only varying 

 in the slopes and thickness of the stone facing according to the extent and 

 situation. 



The whole substratum of tlie valley was water-tight, either from the ex- 

 istence of the solid rock, dense clay, or of hard, compact, mountain gravel; 

 so that there was no difficulty in securing the foot of the puddle. A trench 

 was sunk into the water-tight stratum, whence the vertical puddle vTall was 

 carried up with the bank to the required height. It was 12 feet in width at 

 40 feet below the top, diminishing gradu lly to 8 feet wide at the summit, 

 and was worked in regular layers of 8 inches in thickness. 



The embankments were formed in concave layers 3 feet thick, each layer 

 being completed before another was commenced, steps being cut in the ground 

 where necessary, to receive the layers. 



In order further to secure the tightness of the bank, a lining of peat 15 

 inches in thickness was brought up on the inside of the puddle, and a layer 

 of the same material was laid upon the face of the slope; it was cut small, 

 placed in thin courses like the puddle, and merely trodden down without 

 more moisture than it naturally contained. The author advocates the use of 

 peat in such positions, as, from its light and fibrous nature, in case of a leak 

 occurring, the draught would attract into it all the fibrous particles, which 

 by degrees would stop tlie holes sufficiently for the silt to settle over and 

 eflfectually close the aperture. 



Above the peat a course of gravel 3 feet in thickness was laid, and upon 

 that the stone jntcbing, forming the inner side of the bank. 



The inner slopes were for 20 feet below the top of the bank, 2J horizontal 

 to 1 vertical ; the outer were 2 horizontal to 1 vertical ; where they were 

 deeper than 20 feet, the remainder of the backs sloped 3 to 1 on the inside, 

 and 2J to 1 on the outside. 



All the embankments are 12 feet wide at the top, and 5 feet above the 

 water level. 



The centre of the deepest part of the embankment was traversed by a stone 

 culvert, in which were placed two row* of cast-iron discharge pipes, 18 inches 

 diameter, with suitable valves. A leak was discovered in the centre of the 

 masonry of this culvert, occasioned by the engineer's instructions not being 

 obeyed. The details of the methods employed for remedying this defect are 

 given at length; as also those of the experiments upon cements made by the 

 author after the data given by Vicat. The materials which were most acces- 

 sible for the work were tested veiy carefully, and from the results, it was de- 

 termined to employ mortar composed of rich Manx or mountain lime care- 

 fully slaked, and clay burned with peat in the open air. The proportions 

 were 2h of clay to 1 of lime. They were gromid together, and being mixed 

 with as much water as was necessary, the mortar was used immediately. The 

 mortar for the backing had one measure of sand added ; the grout had two 

 measures of sand in it, and was used thin. 



The concrete was composed of one part of lime, two and a half of calcined 

 clay, and about three jiarts of sharp gravel. 



This cement appeared to set hard, and to be perfectly tight ; but when the 

 reservoir was partially filled, several leaks were discovered, which rendered 

 an examination necessary, and some energetic measures were taken to stop 

 them, all which are described. 



The result of the author's experience seems to be, that mortar made from 

 rich lime and calcined clay, as recommended by Vicat, may set and harden 

 under water when there is little pressure, hut that it is not able to resist the 

 pressure of a considerable depth of water. 



The details of tlie construction of the masonry of the valve house, the fore 

 bay, the waste weir, the bridge of three arches, constructed over the feeder 

 from the river Muddock, and the various feeders for supplying the reservoir, 

 are given at length, with the particulars of the expenditure of the sum of 

 £14,891, which was the cost of the work, exclusive of land compensation, or 

 salaries and professional charges. 



The particulars are also given of a series of observations with rain gauges 

 continued for two years, for the purpose of furnishing data for computing the 

 extent of reservoir which would he necessary to insure a supply of water 

 throughout the year. 



The communication is accompanied by detailed drawings of every part of 

 the works, and a plan of the district in which they are situated. 



" Description of a machine for seioing Flat Ropes." 

 Grad. Inst. C. E. 



By Eugenius Birch, 



In a previous communication, Mr. Birch described and gave drawings of the 

 ingenious machinery invented by Captain Hnddart : tlie subject was uot en- 

 tirely complete without the description of the present machine, which, al- 

 though uot of great importance in a scientific point of view, is well worthy 

 of notice, in consequence of its being attached to this valuable rope machinery, 

 and of its having been worked so successfully. 



It is used for sewing or lacing together ropes, and forming them into flat 

 bands, which are used for mining purposes, &c. 



The bands or flats generally consist of four ropes, which are placed parallel 

 to each other, and paired in contrary directions to the angle of the lay ; being 

 held under an equal degree of tension, they are sewn together with two cords 



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