The present edition of our Instruction Book is in the nature of a revision of our previous publications. It has been our aim to condense and simplify the descriptive matter as much as possible, and at the same time to present a complete description of the parts and their operation in the air-brake and air-signal equipment. In it will be found illustrations and explanations of the new devices, as well as of any modifications of older appliances which have been made with the idea of furnishing the best possible air brake and air-signal equipment. We have distributed many thousand copies of previous editions of our Instruction Book among railway officers and employees in this and other countries, the net result of which has been the education of railroad men in the subject of air brakes, to such an extent that we are led to believe that much of the matter heretofore published can be consistently omitted, especially as there are now many other publications which deal with brake subjects at greater length and provide a source of information in de tail, which may be referred to, if desired. For this reason, the present edition of our Instruction Book has been some what abridged and presents a terse description of the func tions and methods of operation of the devices supplied by this company for the equipment of railroads with its air brake and air-signal apparatus.