November 23, 191 1] 



NATURE 



129 



and it is satisfactory to record that they are now much more 

 constant. The importance of this hermetical sealing is so 

 great when manganin resistances are to be sent to such 

 places as cable stations in the tropics that the attention of 

 instrument manufacturers is directed to the matter. 

 Standard coils are readily sealed, and boxes of coils may 

 be sealed in metal cases. The following figures for 

 standard coils of manganin show the advantage of 

 hermetical sealing : — 



It will be noted that the changes during the last three 

 years are very small. 



Silver Voltameter and Standard Cell, — ^Although the 

 actions which take place when a current passes through 

 a solution of silver nitrate, as in a silver voltameter, are 

 now well understood, the effects of septa — such as silk. 

 filter paper, and porous porcelain — are by no means clear, 

 and experiments have, therefore, been made to decide 

 whether any septum at all should be used in a voltameter. 

 Such experiments were suggested at the Washington meet- 

 ing in 1910. The results of the experiments made at the 

 National Physical Laboratory indicate that a septum of 

 any kind is usually a source of trouble, and may produce 

 secondary reactions during the electrolysis which affect the 

 weight of the silver deposit. Fortunately, voltameters 

 have been designed which render a septum unnecessary ; 

 and these may be useful, not only in precise current 

 measurements with the silver voltameter, but for the 

 d''position of metals other than silver. 



The reproducibility and constancy of the Western normal 

 cell are still being carefully examined. The chief anomaly 

 is the hysteresis effect mentioned in last year's report ; for 

 this effect we have no explanation, although one is much 

 needed, as probably it would enable cells to be made so as 

 to remain even more constant in E.M.F. than at present. 

 It is necessary to point out that while the effect is called 

 a hysteresis one, the E.M.F. does not lag behind the 

 temperature. Briefly put, with ascending temperatures the 

 E.M.F. changes in close agreement with the temperature- 

 E.M.F. formula, but with descending temperatures the 

 E.M.F. changes too rapidly, corresponding to values at 

 temperatures lower than the temperature of the cell by 

 from 3° to 15°. 



The committee had hoped to make this the last 

 report ; but in view of the fact that the republication is 

 not complete, it asks for reappointment, with Lord 

 Rayleigh as chairman and Dr. R. T. Glazebrook as 

 secretary. 



rilE LOCH LEVEN WATER-POWER WORKS.' 



J^HE Loch Leven Water-power Acts were obtained in 



1901 and 1904, authorising the construction of works 



utilise the rainfall of the western slope of Rannoch 



or for power for industrial purposes. 



I he catchment-area for the Loch Leven works is the 



iiasin of the River Blackwater, and is 55 square miles in 



extent, lying between Lochs Treig, Ossian and Rannoch, 



"iH Glen Coe. Rain-gajges established in 1905 and 1906 



•■'• given average readings of more than 70 inches for 



Blackwater basin and 80 inches for Kinlochleven. No 



ipensation-water had to be supplied, this feature greatly 



I' rem abstracts of two papers : (i) The Loch I.even Water-power 

 NVorks, hy A. H. Roherts ; and (2) 'he Hydro-electric Plant in the British 

 ■Aluminuim Company's Factory at Kinloci lev-n, hy F. K. Sonnen^chein, 

 ■ e.-id at the meetini; of the Insiiiution of Civil Kn-inpers on November 14. 



NO. 2195, VOL. 88] 



increasing the available power. The site of the reservoir 

 is favourably contoured for storage purposes, and the full 

 reservoir is about 7^ miles in length and half a mile in 

 breadth. Its greatest depth is 75 feet, and it impounds 

 more than 20,000 million gallons of water. The Black- 

 water dam is 3 112 feet in length, with a maximum height 

 of 86 feet, its top surface being 1068 feet above Ordnance 

 datum. About half its length is formed as a waste-weir 

 in six horizontal steps of 6 inches each. 



The foundation is of an exceptionally sound character ; 

 only a few feet of the surface beds had to be removed to 

 obtain a satisfactory foundation. The dam is built of 

 large blocks of stone embedded in a matrix of ordinary 

 concrete, with fine concrete facework. The valve-tower 

 contains the six valves of the three draw-off pipes, the 

 spindles being carried up to the valve-house above top 

 water-level. The draw-off pipes lead to the upper pen- 

 stock chamber, whence the water is delivered over a 

 measuring weir into the conduit. Water is conveyed to 

 the pipe-track by this conduit, which is 3J miles in length ; 

 it is of square section, 8 feet by 8 feet, and is laid to a 

 general gradient of i in 1000. 



Along the route of the conduit and above the same lies 

 a catchment-area of 35 square miles, with a rainfall of 

 about 75 inches, the greater part of which is drained by 

 three streams. These have been laid under contribution 

 by collecting their water and turning it into the conduit. 

 Electrical transmitters and recorders indicate to the valve- 

 keepers at the lower penstock chamber the changes taking 

 place in the contribution of the side streams, enabling 

 them to take advantage of the extra water and reduce the 

 draw-off from the reservoir, thus storing an equivalent 

 quantity of water in the reservoir. The conduit discharges 

 its water into the lower penstock chamber, of about 300,000 

 gallons capacity, where it is measured and delivered to 

 the pipes as required. 



From the penstock chamber water is conveyed to the 

 power-house in six welded steel pipes of 39 inches diameter. 

 The track is I5 miles in length, and the fall of 935 feet 

 yields a normal static pressure of 406 lb. per square inch. 

 Water is distributed from the six main pipes to the various 

 turbines by a system of pipes comprising two omnibus 

 pipes and six feeders, all of 39 inches diameter. Each 

 " bus " pipe with its three feeders forms one complete 

 system, the two systems being at different levels to enable 

 branches to cross. One branch from each bus pipe feeds 

 each turbine. At the top of the pipe-track, impiediately 

 below the penstock chamber, automatic cut-off valves have 

 been installed to stop the flow of water in the event of a 

 burst occurring on the main pipe-lines. 



The works described have cost about 6oo,oooZ., and are 

 now the property of the British Aluminium Company. The 

 construction was begun in August, 1905, and the factory 

 commenced working in February, 1909. 



.'\s regards the plant erected in the power-house at 

 Kinlochleven, the aggregate power installed is 30,660 horse- 

 power at the generator couplings, the generators being 

 capable of a maximum output of 21,088 kilowatts. Nine 

 main units and two exciter units are erected, each unit 

 consisting of a turbine and two generators. The main 

 turbines are of the Pelton-wheel type, with two water- 

 jets, and are designed to give 3200 B.H.P. as a 

 maximum ; each drives two generators coupled in 

 parallel, and having an output up to 2200 kilowatts 

 together. The two small exciter units are also of the 

 Pelton-whecl type, each driving a pair of generators on 

 one shaft. These consist of an exciter and lighting 

 machine, capable of giving an output up to 550 kilo- 

 watts, and a traction machine up to 94 kilowatts capacity. 

 Efficiency and governor tests were carried out on the 

 main units, and governor tests on the exciter units. The 

 results obtained showed that the turbines did not quite 

 reach their anticipated output, and that their efllciency was 

 slightly below that guaranteed by the makers. The 

 efficiency was improved about 2 per cent, by increasing 

 the area of the lower jet, but keeping the top jet of the 

 original size, and by this alteration the turbines were 

 enabled to give the specified output at the guaranteed 

 efficiency. 



It was found during the tests that the generators were 

 liable to flash over if the voltage increased excessively, and 



