About thirty years ago, M. Estrade, formerly pupil of the Polytechnic School, invented rolling stock for high speed under especial conditions, and capable of leading to important results, more especially with regard to speed. Following step by step the progress made in the construction of railway stock, the inventor, from time to time, modified and improved his original plan, and finally, in 1884, arrived at the conception of a system entirely new in its fundamental principles and in its execution. A description of this system is the object of the memoir. The great number of types of locomotives and carriages now met with in France, England, and the United States renders it difficult to combine their advantages, as M. Estrade proposed to do, in a system responding to the requirements of the constructor. His principal object, however, has been to construct, under specially favorable conditions, a locomotive, tender, and rolling stock adapted to each other, so as to establish a perfect accord between these organs when in motion. It is, in fact, a complete train, and not, as sometimes supposed, a locomotive only, of an especial type, which has been the object he set before him. Before entering into other considerations, we shall first give a description of the stock proposed by M. Estrade. The idea of the invention consists in the use of coupled wheels of large diameter and in the adoption of a new system of double suspension. The locomotive and tender we illustrate were constructed by MM. Boulet & Co. The locomotive is carried on six driving wheels, 8 feet 3 inches in diameter. The total weight of the engine is thus utilized for adhesion. The accompanying table gives the principal dimensions: TABLE I. +---------------------------------------+ | | ft. in. | +-----------------------+---------------+ |Total length of engine.| 32 8 | +-----------------------+---------------+ |Width between frames. | 4 1 | +-----------------------+---------------+ |Wheel base, total. | 16 9 | +-----------------------+---------------+ |Diameter of cylinder. | 1 61/2 | +-----------------------+---------------+ |Length of stroke. | 2 31/2 | +-----------------------+---------------+ |Grate surface. | 25 sq. feet. | +-----------------------+---------------+ |Total heating surface. | 1,400 sq. ft. | +-----------------------+---------------+ |Weight empty. | 38 tons. | +-----------------------+---------------+ |Weight full. | 42 tons. | +---------------------------------------+