August io, ign] 



NATURE 



20 1 



above that of the reservoir level. The six pressure lines 

 are composed of welded pipes 307 inches external 

 diameter, and have a thickness varying between 0-39 and 

 11-s- imh. The maximum static head is 1417 feet. The 

 turbines are Escher, Wyss and Co. 's impulse wheels, each 

 designed to generate S200 horse-power at 300 revolutions 

 per minute. 



The company has greatly increased the water available 

 by diverting the Texcapa, Tenango, Nexapa, and Xalte- 

 puxila Rivers into the Necaxa reservoir by means of an 

 extensive system of tunnels through the dividing ridges. 

 The catchment area has thus been raised to 154 square 

 miles, and can shortly be further increased by another 

 77 square miles by bringing in the large Laxaxalpan 

 stream. The present storage capacity of the entire system 

 is about 4220 million cubic feet of water. 



As a first step to enlarging the power-house, the capacity 

 of each of the existing six turbines has been raised to 

 11,000 horse-power by fitting new runners and new nozzles. 

 The velocity of the water in each of the six pipe-lines 

 was thereby increased to the exceptionally high figure of 

 18 feet per second, a velocity which has not been found to 

 be injurious in any way. Two new units of similar design 

 and by the same makers have been installed ; these are 

 each of 16,000 horse-power, and are supplied with water 

 through a new pipe-line system. The total capacity of the 

 station is now 98,000 horse-power. The electrical energy 

 is transmitted a distance of 93 miles to the city of Mexico 

 and to other towns. 



The power works of the Rio de Janeiro Tramway, Light 

 and Power Co. are supplied from the largest artificial 

 reservoir formed by a dam wall at present in existence. 

 It has a total volume of 7S40 million cubic feet. The 

 length of the lake is 17 miles. The dam is of the arched 

 concrete type. The gross maximum head at the power- 

 house is 1015 feet. There are six impulse-wheel turbines, 

 built by Escher, Wyss and Co., each generating 9000 horse- 

 power .it 300 revolutions per minute. The generators 

 supply three-phase current at 6000 volts and 50 cycles, 

 which is stepped up through transformers to a line voltage 

 of 88,000 for transmission to Rio de Janeiro, the distance 

 being 55 miles. 



Some very difficult work had to be carried out on 

 the pipe-line of the power-plant at Tyssedalen, near 

 Odda in Norway. The Ringedals Lake provides an 

 ideal natural storage reservoir at an elevation of 

 1426 feet above and 2-17 miles distant from the fjord 

 at the edge of which the power-station is situated. A 

 regulating tunnel from the Ringedals Lake discharges into 

 the little Vetle Lake immediately below, which forms a 

 second small regulating basin. A tunnel 11,200 feet in 

 length passes through the mountain to the penstock 

 chamber, from which the pipe-line leads down to the 

 power-house. The tunnel is driven through granite for 

 the whole of its length, and was completed in two years. 

 The erection of the pipe-lines was work of a very difficult 

 character. The total length is 2360 feet, and the pipes 

 reach an angle to the horizontal of 55 degrees. 



A typical high-pressure power-station in Switzerland is 

 that of the Kraftwerk Brusio Company, which utilises the 

 water of the Poschiavino River in the Canton Grisons on 

 the south side of the Alpine chain. About 55,000 horse- 

 power are developed, the greater part of which is trans- 

 mitted to the industrial districts of northern Italy over a 

 transmission line of 93 miles. The total head available 

 is about 32S0 feet, and is used in two stages. The upper 

 lies between the Lago Bianco, on the Bernina Pass, and 

 the Lago di Poschiavo, giving an effective head of 1070 

 feet for the Robbia station. The lower is between the 

 Poschiavo Lake and the Italian frontier at Campo Cologno, 

 where the head obtained is 1375 feet. 



The River Siagne rises in the Alpes Maritimes province 

 of south-eastern France to the north of Cannes. A power- 

 station is situated near the village of St. C^saire, and 

 utilises a fall of about 1142 feet of the Siagne; about 

 14,000 horse-power are available. The high-pressure pipe- 

 lines of this plant have demonstrated in a most drastic 

 manner what the consequences of incorrect design can be. 

 The original pipe-line had to be abandoned after a few 

 months' running on account of unsatisfactory working of 

 the plant, and an entirely new pipp-Iine had to be built on 



no. 2180, vol. 8;] 



totally different principles, in spite of the fact that the 

 chief dimensions of the pipes were perfectly correct and 

 amply sufficient for the conditions of head and discharge, 

 and, moreover, were not altered in the second pipe-line. 

 The principal faults were owing to the following : — 

 (1) Too great a length of the upper portion, under low 

 pressure, with pipes of small thickness, whereby a con- 

 tinual working or respirating phenomenon became apparent 

 in this part of the pipe-line. (2) Insufficient fixing or 

 anchoring of the pipes in the lower portion of the line, 

 and a most curious position of the distributing pipe, in 

 which very harmful vibration, combined with displacement 

 of the pipes, could take place on sudden variations of 

 water velocity or shocks in the pipe-line ; this might easily 

 lead to a burst, especially in the case of riveted pipes. 

 (3) Unsuitable dimensions of the connecting pipes between 

 the distributor and the turbines, with their length too great 

 and their diameter too small, resulting in considerable 

 accentuation of the pressure variations. 



French engineers in general build pipe-lines without 

 expansion joints ; a large number of such high-pressure 

 pipe-lines are now in continuous operation in France. 

 This design must be characterised as irrational, especially 

 in view of the demands made at the present day on the 

 pipe-line of a central station with continually and rapidly 

 changing water velocities. 



THE SCIENTIFIC STUDY OF NAVAL 

 ARCHITECTURE IN GERMANY. 1 



TT may sound strange if, in the land of ships — the land 

 that has probably done most towards the practical and 

 scientific development of the whole domain of shipbuilding — 

 I take upon myself to describe the aims of scientific study 

 in Germany and the methods which it is now adopting. 



Apart from small unimportant beginnings, the real 

 nursery for scientific study in the various domains of naval 

 architecture in Germany has been the institution now 

 known as the Konigliche Technische Hochschule zu Berlin, 

 in Charlottenburg. Since 1904 the Konigliche Technische 

 Hochschule in Danzig has likewise taken part in this 

 work. The naval architectural departments of both these 

 colleges have the same end in view, namely, the training 

 of the young men who will later in life take a successful 

 part in the building of the mercantile and naval fleets of 

 Germany. 



In accordance with the system adopted in all the technical 

 colleges in Germany, it is a preliminary requirement for 

 the admission of the students to the Charlottenburg tech- 

 nical college, that they should have passed the matriculation 

 examination of a Gymnasium, Realgymnasium, or Oberreal- 

 schule. As these schools comprise nine forms, it follows 

 that candidates for admission to technical colleges must be 

 between eighteen and nineteen years of age. Since a further 

 qualification is a practical training of one year at a shipyard 

 of recognised standing, the age of the candidate is increased 

 by six months — often by a whole year. To this must be 

 added the period of military service, which is required of 

 every physically and mentally sound German citizen, but 

 which, in the case of an educated man who has obtained 

 his volunteer certificate, is restricted to one year. For 

 those who contemplate a career in the higher ranks of the 

 Imperial naval construction department, the period of 

 practical work and the year of service are spent in naval 

 establishments, that is to say, in an Imperial dockyard and 

 on board a naval training ship respectively, before the 

 course of study at the technical college is entered upon. 

 It may thus be said that the course of study begins when 

 the student is twenty-one, and that it has been preceded by 

 a certain period of preparation in the practical work of 

 shipbuilding or marine-engine building. 



The course of instruction is arranged in the following 

 manner : — Within the department for naval architecture a 

 distinction is made, in the first instance, between the pro- 

 fessions of naval architect and marine engineer. The course 

 of instruction itself in almost all the subjects comprises 

 lectures and tutorials or "practices," the object here kept 

 in view being that what is taught in the former is put 

 into practical'shape in the latter. It is a general principle 



1 From apioer read before the Institution of Naval Architects on July 

 by Prof. O. Flamm. 



