The author has long been in the habit of using charts to aid him in his work. Knowing the value of them in saving time, simplifying work and ensuring correct calculations he feels confident that they will be appreciated by engineers, architects and contractors, for whose benefit they have been compiled. Care has been taken to make the charts as clear and as easily understood and, above all, as accurate as possible. They have been based upon theoretical considerations, modified by what is considered to be good practice in this country. CHART 1.--This chart is for determining the number of square feet of heating surface of a low pressure steam heating system, pressure not to exceed 5 lbs. per square inch by the gauge, necessary to supply the heat lost through the various kinds of wall surfaces of rooms. The chart is divided into four parts. CHART 2.--For determining the diameters of the supply and return pipes for a heating system. CHART 3.--For finding the number of square feet of boiler heating surface and the number of square feet of grate surface for a boiler that is to supply steam to a steam heating system. CHART 4.--For determining the area of the cross section of a square flue, or the diameter of a round flue, leading from an indirect radiation heater to the register in a room to be heated. Full details are given for the use of these cards. These four charts are printed on heavy white card-board and bound together with cloth, size 13 in. by 9-1/4 in., $1.00[++]. _These cards are securely packed for mail and sent to any part of the World on receipt of price._ * * * * * Gas Analyst's Manual. By JAQUES ABADY, M. Inst. Mech. E. _(Incorporating F. W. Hartley's "Gas Analyst's Manual" and "Gas Measurement.)"_ EXTRACT FROM PREFACE. The numerous requests received by the Publishers for the late Mr. F. W. Hartley's "Gas Analyst's Manual" and "Gas Measurement" form the justification of the present work, which embodies practically the entire contents of those two volumes. It has been found, however, that their scope was too narrow to comply with modern requirements in various directions, although ample at the time they were written, and so I have ventured to add such extensions as appeared to be necessary in order to meet the demand which exists for a comprehensive work on Gas Apparatus and its use. This large work has been in course of preparation for the past three years by Mr. Jaques Abady, and has been very carefully revised by other experts. Many valuable tables of data have been included, a number of which come from the private note books of the Author, being practically results obtained by him during many years of work as Expert, Gas Engineer and Gas-Works Materials Manufacturer. CONTENTS OF CHAPTERS.