THE IKRIGATION AGE. 



25 



Ropp's New Commercial 

 Calculator 



and Short-Cut Arithmetic 



REVISED, ENLARGED 

 and IMPROVED 



HAS MORE THAN TWICE THE 

 CAPACITY OF FORMER EDITIONS 



The Correct Answer Instantly Found 



to All Practical Problems That 



Occur in the Store, Shop, 



Farm, Bank or Office 



Will Prevent Mistakes, Relieves the 



Mind, SAVE Labor, Time, 



Money and Do Your 



Figuring in the 



Twinkling of 



an Eye. 



POCKET-BOOK STYLE 

 Price, S1.OO 



Shows the Answer as Quickly as a Watch shows 

 the Time to all Problems likely to occur in the Office, 

 Store, Shop, Bank, Farm or factory. 



Wf Ask for the late Copyright Tenth Revised, Enlarged 

 and Improved Edition. Has more than twice the con- 

 tents, scope and capacity of earlier editions, of which 



OVER TWO MILLION COPIES 

 HAVE BEEN SOLD 



An entirely new system of Labor-saving Table and easy 

 Methods of Calculation. Explains and simplifies every 

 principle in Arithmetic, Mechanics and Mensuration. It 

 will make the study and handling of Figures quite easy and 

 interesting for all. It will prove a boon to all whose edu- 

 cation in Arithmetic is limited or neglected. It will enable 

 anyone to become expert in Arithmetic and a rapid 

 Calculator. It is the most complete and practical work on 

 Figures ever published lor the masses. It is the con- 

 summation of devising and improving system after system ; 

 of expending thousands of dollars in experimenting ; of 

 making millions of miscellaneous calculations, and of do- 

 ing some vigorous thinking by an analytical, practical and 

 persevering mind. 



The New Commercial Calculator is 6J/2 inches long 

 and 3% inches wide. It has 160 pages printed from new 

 plates on a superior quality of white book paper. The cloth 

 binding is in a fine quality of book cloth with turned-in 

 edges, and title in black ink. The Pocket-Book style is 

 bound in water-proot Moroccoline (more durable than real 

 leather), and has pocket, flap, silicate slate and title in gold. 



A copy of this work will be mailed to 

 all new or renewal orders to the 

 Irrigation Age. $1.OO covers the cost of 

 subscription to Age for one year and a 

 cloth bound copy of this work. 



ADDRESS 



SUBSCRIPTION MANAGER 



The Irrigation Age 



3O N. Dearborn St. Chicago 



Ready Now: The Primer of Hydraulics 



By FREDERICK A. SMITH, C.E., Hydraulic Engineer 



When writing to advertisers 



This new book is a splendid volume of over 200 pages of 

 absolutely new matter pertaining to the subject of Hydraulics 

 and its allied branches. All the subjects treated of are han- 

 dled in a simple and practical way to make them of use to the 

 men who have been unable to obtain a college education, but 

 who are successful practical men in fields where they require 

 a knowledge of the principles of Hydraulics and instructions 

 how to solve their problems in a simple and satisfactory 

 way. This book is indispensable for anyone engaged in 

 works relating to Hydraulics, Irrigation or Drainage; it 

 is primarily designed for the practical man in the field, 

 but will be equally welcome to the trained Hydraulic 

 Municipal and Railroad Engineer especially, on account of the 

 many valuable tables compiled by the author, which will save 

 a tremendous amount of time in computations. 

 Condensed Table of Contents. 

 General Properties of Matter. 

 Algebraic Principles. 

 Geometrical Principles. 

 Trigonometry. 



Mensuration of Plane Figures. 

 Mensuration of Solids. 

 The Principles of Mechanical Forces. 

 The Three States of Matter. 

 General Hydraulic Principles. 

 The Coefficient of Roughness. 

 How to calculate n. 

 Explanation of the "C" Tables. 

 Open Channels Problems. 

 Closed Channels Problems. 

 Pipes Flowing Full Under Pressure. 

 Loss of Head by Enlargement of Channel. 

 Subdivisions of Channels. 

 Loss of Head at Entrance to Pipes. 

 Ditches. 



Ditch Tables and Their Applications. 

 Flow Measurements. 

 The Use of Logarithms. 



Tables. 



Fourteen tables giving the factor C for all cases of chan- 

 nels for a coefficient of roughness ; w varying from 

 008 to .050, inclusive, for channels having a hydraulic 

 radius from .01 ft. to 900.0 and for slopes varying from 

 0.1 to .000025, thus practically covering every possible 

 condition. 



Tables of square roots of numbers used for r and s. 

 Table of Hydraulic Elements of the Circle. 

 Table of Hydraulic Elements of Composite Section. 

 Table of Areas and Circumferences of Circles. 

 Table of Hydraulic Equivalents. 



Table of Weights of a Cubic Foot of Various Substances. 

 Conversion Table of United States and Metric Measures 



and Weights. 



Table of Squares, Cubes, Square Roots and Cube Roots. 

 Table of Logarithms. 

 Table of Natural Sines and Cosines. 

 Table of Natural Tangents and Cotangents. 

 Conversion Table, millions of gallons in 24 hours in other 



units. 



Table of sizes of pipes or cylindrical conduits required for 

 the flow of given quantities of water at given veloc- 

 ities. 



Most all of these taoles have been originated and 

 computed by the author and have been checked in prac- 

 tical work and found to De correct, so that the tables alone 

 will be worth many times the cost of the Dook. 



The price of the book has been placed as low as is 

 consistent with the superior quality of the work and it 

 may be obtained on the following terms: C2.50 a single 

 copy, cloth bound; if order is sent with a new subscrip- 

 tion to Irrigation Age or a renewal subscription, the 

 book will be sent and the Irrigation Age one year for 

 the sum of $3.00. 



Postage is included in the above prices. 



Send in your orders early, so as to receive early attention. 



Send all orders and remittances to 



irrigation Age, 30 N. Dearborn St., Chicago, 

 please mention The Irrigation Age. 



