The Glass Goes West

One morning last week scientists, foremen and loyal workmen at Corning (N. Y.) Glass Works looked anxiously up at a grey, wintry sky, hoped the threat of snow would not materialize, for momentous and delicate doings were on foot. The snow held off.

Beside the company's railroad spur stood a mammoth flat-topped trailer. Flat on the trailer lay a circular crate, nearly 18 ft. across, made of reinforced sheet steel. Inside, protected by close-packed felt and rubber, was the biggest and costliest piece of glass in the world -- the 200-in. telescope mirror destined for California Institute of Technology, 3,000 miles away. For nearly a year, since it was formed of molten pyrex borosilicate glass, the great disk had cooled slowly in its annealing oven. In the testing plant it had been pronounced fit for its job. 'Now it was ready for shipment. It weighed 20 tons, its complicated packing case 15 tons more. The trailer which brought it to the rail spur had taken 30 hours to move a quarter-mile.,

On the track waited a specially-built freight car. Flat and without sides, it was so cut down in the centre that its bottom was only 5^ in. above the rails. Its wheels were only 26 in. in diameter instead of the standard 33 in. A huge railroad crane lifted the mirror slowly to a vertical position, swung it clear of the trailer. Inch by inch it was lowered into the railroad car. For a half-hour it was allowed to settle comfortably into the recess. Then the New York Central Railroad man telephoned his home office that the loading was complete.

This week the mirror starts its journey west on a special train carrying a freight-car with equipment for unloading, and a caboose. The train will travel no faster than 30 m.p.h. Since it was impossible to provide a lateral clearance of 18 ft., the mirror had to be shipped standing upright. This raised the problem of overhead clearances. After much study a route was worked out with the tightest squeeze a three-inch bridge clearance at Buffalo. The big disk goes by New York Central to Cleveland; by Cleveland, Cincinnati, Chicago & St. Louis to St. Louis; by Chicago, Burlington & Quincy to Kansas City; by Atchison, Topeka & Santa Fe to Pasadena, Calif. There in Caltech's laboratories, where a huge grinding machine has been set up, it will spend some three years acquiring the ideal paraboloid curve in its face. Some time before 1940 it will be installed in its telescope on Palomar Mountain in Southern California.

In 1928 Caltech was granted $6,000,000 of Rockefeller money for the telescope, with the stipulation that full opportunity to cooperate be given to Carnegie Institution's men at Mt. Wilson Observatory. The committee in charge of the project is headed by Mt. Wilson's venerable George Ellery Hale, famed solar authority. The first 200-in. mirror was marred during the casting when cores broke loose from the floor of the mold and floated to the top of the molten glass (TIME, April 2, 1934). Rather than grind out the huge pockmarks in the mirror's back, the Corning physicists decided to cast a new disk.* Second time the cores stayed in place.

Responsibility for the safety of the mirror passed to the railroads last week the moment the special train was coupled. One thoroughgoing wreck would set U. S. Astronomy back three years.

* The holes and grooves in the mirror's back not only diminish the total weight but provide a hold for the steel grips which will keep the mirror in place in the telescope.

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