Dynamical engineering can be divided into mechanical engineering, which covers the construction of all prime motors, the transmission of power, and the use of machines and machine tools. Closely allied is electrical engineering, the art of the transformation and transmission of energy for traction, lighting, telegraphy, telephoning, operating machinery, and many other uses, such as its electrolytic application to ores and metals. Then we have the combined application of statical, mechanical, and electrical engineering to what is now called industrial engineering, or the production of articles useful to man. This may be divided into agricultural, mining, metallurgical, and chemical engineering. Surely this is a vast field, and can only be hastily described in the sketch which we are about to give. STRUCTURAL ENGINEERING This is the oldest of all. We have not been able to surpass the works of the past in grandeur or durability. The pyramids of Egypt still stand, and will stand for thousands of years. Roman bridges, aqueducts, and sewers still perform their duties. Joseph’s canal still irrigates Lower Egypt. The great wall of China, running for fifteen hundred miles over mountains and plains, contains one hundred and fifty millions of cubic yards of materials and is the greatest of artificial works. No modern building compares in grandeur with St. Peter’s, and the mediæval cathedrals shame our puny imitations. These mighty works were built to show the piety of the Church or to gratify the pride of kings. Time and money were of no account. All this has now been changed. Capital controls, and the question of time, money, and usefulness rules everything. Hence come scientific design and labor-saving machinery. The engineer of our modern works first calculates the stresses on all their parts, and proportions them accordingly, so that there is no waste of material. Hand labor has given place to steam machinery. All parts are interchangeable, so that they can be made and fitted together in the least possible time, as is seen every day in the construction of a steel-framed office building. Our workmen receive much higher wages than in the past, while time and cost have been diminished. RAILWAYS The greatest engineering work of the nineteenth century was the development of the railway system which has changed the face of the world. Beginning in 1829 with the locomotive of George Stephenson, it has extended with such strides that, after seventy years, there are 466,000 miles of railways in the world, of which 190,000 miles are in the United States. Their cost is estimated at forty thousand millions of dollars, of which ten thousand millions belong to the United States.