Sir,-Mr. Bolton has recently pointed out in your columns that in an article dealing with the solution of continuous ridged portal frames, no example with a north light type of roof or with unsymmetrical load on the rafters was given, and goes on to say that the calculations of fixed-end constraints and of the effect of unit operations for such conditions makes a solution much more difficult.
In this paper it is intended to survey generally the history and development of the power station industry which began in 1831 with a few simple discoveries and in a relatively short space of time became one of the primary factors in all spheres of modem life and perhaps the greatest single source of motive power, industrial and domestic. It is a tribute to all those who have shared in building up so great an enterprise that practically all essential processes have: made themselves dependent upon electrical energy. There is hardly a comer of the world so remote as not to have come under its influence. Engineers can look back on the glory of past achievements with pride, and forward with confidence to the almost superhuman efficiency of the first atomic station. Uskmouth Station, with many others now building, is a good example of the extento which practice has followed theory in our own day. B.A.E. Hiley
In 1950 the Ministry of Works called for competitive designs and estimates for eight prestressed concrete tanks, each tank to have a capacity of 430,000 gallons, with a maximum depth of liquid of 33 feet, giving an internal diameter of 50 ft. o in. Colonel A. Raymond Mais
The distribution of stresses in old and new concrete in compound sections is examined for an instantaneous load, after which the redistribut.ion of stresses under sustained load and shrinkage is described. The redistribution of stress which takes place in statically indeterminate structures when their individual members are cast independently and connected later is discussed. Professor Dr. Ing. H. Craemer