“A SECTION OF LONDON’S FIRST AUTOMATIC EXCHANGE - at Holborn. The apparatus is part of the Tandem exchange which transmits calls from one manual exchange to another, thus effecting a considerable saving in time.”
More than a thousand million telephone calls were made during 1936 in the London area alone. The modern automatic exchanges which made this possible are marvels of ingenuity. This chapter describes the workings of the automatic telephone. The modern telephone exchange is a wonderful place, and represents the triumph of a highly specialized branch of electrical engineering. The magnitude of the task which is daily performed by the telephone system can be realized when we consider that in the area known as the London Tele-communications Region, over a thousand million telephone calls were dealt with in 1936. This chapter by Howard Barry explains how this amazing task is carried out.
Fifth Avenue, New York
“FIFTH AVENUE, one of the main thoroughfares of New York, appears almost to be a trench, so dwarfed is it by the huge buildings. The Empire State Building, dominating the scene, towers to a height of 1,250 feet. It is built on the site of the old Waldorf-Astoria Hotel, at the corner of Fifth Avenue and 34th Street.”
From the accidental discovery that selenium was sensitive to light has developed a wide range of instruments and equipment which the engineers can use to assist him in his work. In 1873, a scientist named Willoughby Smith was using selenium as a resistance in an experiment with telephone receivers. In this experiment it was discovered incidentally and accidentally that the selenium was affected by light. This discovery released a flood of inventions, and the evolution of photoelectric and light-sensitive cells is described in this chapter by T J Fielding.
The skyscrapers of New York and other American cities rise to heights of 500 feet or more above the level of the streets. These giant buildings have been evolved with the object of solving modern problems of congestion. We have seen how the mechanical engineer has made possible the growth of huge industries. These industries and the organization they involve have caused a remarkable growth in the population of large cities. This has given rise, in such cities as New York particularly, to a new problem - how to accommodate these masses of people in a comparatively confined space. Nowhere in the world has that problem been of more importance than in Manhattan with its huge daytime population. New York could not be extended laterally in the same way as London, for instance, and it seemed that the only way that expansion could be carried out was upwards. Engineers, therefore, as many as fifty years ago, considered the possibilities of building the tall structures which we now know as skyscrapers. Yet there are definite limits to the height of a building. Foundations will support only a definite weight, and to go on adding stories to the building will only increase the weight until the point is reached when the foundation will no longer hold it. In addition, for the lower stories to support the weight of the upper ones without being themselves crushed, they must be thick and strong, thus adding even more to the weight which the foundations have to support. The highest stone structure yet built is the Washington Monument, which is 555 feet high. This is not far from the limit of height which it is possible to reach with masonry. Yet engineers have succeeded in raising buildings in New York to twice that height, and they maintain that it would be possible to build to a height of 3,000 feet and even more. It is the engineer who has enabled the architect to design such skyscrapers. This is done by the use of a strong steel frame, and so when we see a modern building erected, the steel frame or skeleton is the first to go up. The building of these skyscrapers is a story of outstanding interest. Some of my readers may not at first associate the building of a skyscraper with engineering, but there will be no doubt left in their minds when they read this chapter, which is illustrated with a magnificent photogravure section. Here, Lieut-Commander R. T. Gould will describe the problems with engineers have overcome in the building of famous skyscrapers in America.
On the Twenty-Fifth Floor of the Federal Building, New York
“ON THE TWENTY-FIFTH FLOOR of the Federal Building, New York, workmen swing in a load of granite from a crane. In building skyscrapers the steel frame is first completed to its full height. Then the floors and walls are built round the towering skeleton of steel.”
Building a Pier for the Little Belt Bridge
“BUILDING A PIER for the Little Belt Bridge. For the foundation of each pier a cellular cofferdam was sunk and filled with concrete. The piers were built of concrete and from them the spans were cantilevered out until they met.”
The Complexity of the Automatic Telephone System
“THE COMPLEXITY OF THE AUTOMATIC TELEPHONE SYSTEM is shown by a relatively small bank of apparatus at a modern exchange. The illustration shows “directors” being inspected at the Pollards exchange, near Norbury, London. Directors translate the three letters dialled by a subscriber and transmit an appropriate series of impulses along the first free line to the desired exchange.”
Near the site of a former barrage, built thousands of years ago, desert lands of Iraq have been made fertile by the building of a barrage to control the refractory waters of the River Euphrates. This chapter, by Harold Shepstone, describes the building of the Hindiya Barrage. The chapter is concluded in part 18 and is the sixth article in the series Triumphs of Irrigation.
Selectors in Action
“SELECTORS IN ACTION for a call to a subscriber whose telephone number is 2343. On the left is the “thousands” selector; the central unit selects “hundreds” and the “tens and units” selector is on the right.”
Links Between Two Subscribers
“LINKS BETWEEN TWO SUBSCRIBERS, SHOWN IN SIMPLIFIED FORM. The line switch selects the first disengaged unit of the automatic apparatus, and the three selectors find the number by stages, as shown in the diagram above.”
The World’s Highest Buildings:
“1,250 FEET ABOVE THE STREET is the airship mooring mast at the top of the Empire State Building. Tall as are the other buildings in the neighbourhood of Fifth Avenue, they are all dwarfed by this colossal structure. It was built in accordance with the zoning laws of 1916, by which only a quarter of the available site may be built up to any height desired. At prescribed heights, too, the building line must be stepped back a specified amount.”
The World’s Highest Buildings:
The Skyscraper District (1)
“THE SKYSCRAPER DISTRICT of New York is centred at the south of Manhattan. In the background of the photograph are the Brooklyn and Manhattan Bridges across the East River.”
“THIRTY-ONE STORIES HIGH, the RKO Building, one of the group in the Rockefeller Center, rises to a height of 409 feet. This photograph shows how the steel skeleton and the floors are completed before the walls are built up. The RCA Building, the highest in the Center, has seventy stories and reaches to 850 feet.”
Automatic Printing of Photographic Negatives
“AUTOMATIC PRINTING of photographic negatives is made possible by the aid of the photoelectric cell. The photoelectric printer, as the machine is called, automatically ensures perfect prints regardless of the character of the negative.”
A Photoelectric Exposure Meter
“A PHOTOELECTRIC EXPOSURE METER is incorporated in the automatic photoelectric printer so that, while one negative in a strip is being printed, the correct exposure necessary for the next is recorded automatically according to the density of the negative. The machine also automatically selects the type of paper required for a good print of any particular negative.”
The Hindiya Barrage
“THE UPSTREAM FACE of the Hindiya Barrage before water from the Euphrates was diverted into the new channel across which the barrage was built. The navigational lock, seen in the left foreground, is 26 ft 3 in wide. It is divided by gates into two sections, each 164 feet long. The walls of the lock are of brickwork, 26 ft 3 in high and 10 feet thick.”
Building the Hindiya Barrage
“HUGE ROLLS OF REEDS were used to dam the old stream of the Euphrates and divert it into the new channel. The rolls, or “sausages” as they were called, were about 60 feet long. They were pushed into the water and sunk in position by weights. Then brushwood, stones and earth were thrown upon them to form a dam about 70 feet wide across the river.”
“THE BED OF THE RIVER was artifically built up above and below the Hindiya Barrage. On the downstream side a weir, 8 feet wide, was built across the channel. The weir was built on a concrete foudnation. The piers of the barrage are built in a series of fours teps on the downstream face, reducing the length from 43 feet at the bottom to 36 feet at the top.”