It was at one time supposed that the railroads would be able to carry freight so much cheaper and quicker that the canals would gradually become useless, and only the heaviest and most unimportant class of goods would be sent from place to place over the all-water inland routes. One of the reasons for this was that the canals had not advanced in any way since they were first built--that is, the mechanism of locks had not been improved, and no other methods had been devised by which canal traffic might be made speedier. But about six years ago an American engineer, Mr. Chauncey N. Dutton, invented a lock which many experts think will probably revolutionize canal traffic, and make it possible to build a waterway from New York to the Great Lakes, following the line of the Hudson and using Lake Champlain and the St. Lawrence River. The lock invented by Mr. Dutton is founded upon the already well-known and widely utilized principle of compressed air, and although at first it looks complicated to the average person, it is said by mechanics and engineers to be a very simple affair. The lock is called a pneumatic balance lock. It is made up of two sections, each of which may very well be compared to elevators. These elevators are in reality huge tanks, each about 510 feet long, 65 feet wide, and capable of holding 26 feet of water. These tanks are placed in other steel tanks which correspond to the shafts of an elevator, and these shafts are placed alongside of one another. Of course the shafts of these great elevators are sunk as deeply into the earth as it is necessary to raise a ship into the air, or up to the higher level of the canal. The sunken portions of the shafts are filled with water, and the tanks, or elevators, are arranged so that they work up and down like balanced scales--that is, when one is at the higher level the other is at the lower level. Compressed air does all the work. Perhaps by looking at the diagram this may be more clearly made apparent. [Illustration: DIAGRAM OF LOCKS.] The two tanks are connected by a great pipe 21 feet in diameter. Where it connects immediately with the locks this pipe is flexible and moves up and down with the tanks, and looks very much like a huge elephant's trunk. Through it the compressed air shifts, at the will of the operator, from one shaft to the other.