The testing-table is one of the most interesting of Altoona's activities. The engine is run upon a series of wheels that fit exactly underneath its own; it is fastened snugly into place; connections are made with a score of pipes and rods that fit upon its mechanism, and it starts off for a run up over the division. It runs miles and miles, snorting furiously over the hard grades and under the heavy loads it has to haul, and yet it does not move even the finest fraction of an inch from that testing table. Its mechanism throbs with energy, its wheels revolve at a fearful rate; yet it is a helpless caged creature in a seemingly impotent energy, as the men in charge of the test watch a dozen dials, notebooks in hand. The big driving wheels turn only upon the friction wheels beneath them but the engineers who are conducting the test can tell the speed at which the locomotive is travelling--in theory--by the almost human needles upon the dial-faces. There is more delicate scientific apparatus behind the engine. It is stripped from its tender for this test, and by this apparatus the pull of the engine upon the dead load of the train can be exactly estimated in pounds and ounces. Nor is this all. The friction wheels underneath the drivers are controlled by powerful water brakes, and by the regulation of these brakes, strains or handicaps can be placed upon the engine exactly similar to those of the grades it may have to reach over a heavy mountainous stretch of railroad. There is no guess-work about modern railroading. Many hundreds of thousands of dollars are spent each year in expert scientific tests of every sort, in the salaries of men who devote their entire time to this work; and the railroads reap the benefits in many more hundreds of thousands of dollars in operating economies. Railroading is a pretty exact science; the big engine on the testing-table at Altoona is only one of a host of evidences of the skill and genius that are being brought to bear upon the operation of the great railroad properties of the country at the present time. This engine goes upon diet. Dr. Wiley down at Washington with his young men sustaining themselves scientifically upon measured and selected foods has something of the same method that is shown with the test engine up at Altoona in the hills. Its supply of coal is carefully weighed and analyzed by sample. An accounting of the amount consumed down to ounces is carefully kept, the water supply is also examined and measured with great care. When the test is finished and the big chaotive engine has covered miles of theoretical grades with a long theoretical train hitched on behind, the experts get busy with their pencils and begin to prepare the reports upon which their chief may rely when he goes ahead to construct another gross of 100-ton locomotives. * * * * *