MECHANICAL ENGINEERING, THE PROGRESS OF. 



543 



The experiments made for the Prussian Gov- 

 ernment by Wohler and Spangenberg during a 

 period of fifteen years, and concluded eightyears 

 ago, are just becoming known to practicing 

 engineers; and Wohler's law, and Launhardt's 

 and Weyrauch's analyses of results, are found 

 valuable checks upon usual methods of propor- 

 tioning iron parts of structures. Not simply 

 tha load to be applied, but the frequency and 

 the method of its application, and the condi- 

 tion of the structure as determined by earlier 

 strains, must be considered in settling upon its 

 dimensions, and upon the magnitude of the fac- 

 tor of safety. Nevertheless, these quantities are 

 well covered by the factors of safety that have 

 become generally accepted. 



Perhaps the most important advance made 

 in the use of materials in engineering has been 

 the general introduction of systematic inspec- 

 tion and careful testing of materials. Such 

 inspection and test is now demanded by every 

 well-drawn specification, and is carried out 

 usually by trained and skillful inspectors. 

 Well-managed establishments have organized 

 departments devoted to the examination and 

 test of materials. 



A method of inspection which will safely 

 determine the value of each piece to be put 

 into a structure or machine is becoming adopt- 

 ed ; and soon every part of each bridge or ma- 

 chine upon the strength of which depends safe- 

 ty of life and property will have to be proved 

 by actual test before use. The great testing- 

 machine at Watertown Arsenal, set up by the 

 defunct board appointed in 1875 to test iron, 

 steel, and other metals, is at the service of the 

 public. 



The consumption of iron and steel is the 

 truest measure of the magnitude and value of 

 the work of mechanical engineering in the 

 United States. The growth of the iron manu- 

 factures of the United States has all occurred 

 since A. D. 1700, when there was not a blast- 

 furnac3 in this country, and principally since 

 the year 1794, when the first steam-engine was 

 erected in America, eighteen years after James 

 Watt made his famous improvements. To-day 

 there are over 1,000 iron and steel works in the 

 United States, employing $230,000,000 in cap- 

 ital as against $122,000,000 in 1870-71, pro- 

 ducing 7,250,000 tons of iron and steel, just 

 double the production of 1870, and employing 

 nearly 150,000 men. The value of all products 

 is not far from $300,000,000, and wages amount 

 annually to about $55,000,000. In ten years 

 Massachusetts has increased her product 65 

 par cent, West Virginia 104 per cent, Alaba- 

 ma 800 per cent nearly, Georgia 125, and 

 Tennessee 125 per cent. Pennsylvania holds 

 her place at the head of the list, producing 

 3,500,000 tons per annum ; Ohio makes 1,000,- 

 000 tons, New York 600,000, Illinois 400,000, 

 New Jersey 250,000, and other States smaller 

 amounts. 



Since 1870 the weight of pig-metal produced 

 has increased from 2,000,000 to 3,750,000 tons 



per annum, or 84 per cent ; rolling-mills make 

 2,500,000 tons of rolled iron, an increase of 

 two thirds; the Bessemer steel manufacture 

 has grown from less than 20,000 tons in 1870 

 to 900,000 tons in 1881 ; open-hearth steel is 

 now reported at about 95,000 tons, an industry 

 unknown in this country in 1870. Of crucible 

 steel 70,000 tons are made per annum, a gain of 

 150 per cent in the decade, and its applications 

 are extending day by day. 



But Great Britain still remains at the head 

 of iron-making countries, turning out 8,000,000 

 tons of pig-iron during the year, an increase of 

 one third since 1870, and the increase still con- 

 tinues. The weight of Bessemer rails made has 

 reached above 700,000 tons, and of Siemens- 

 Martin steel 250,000 tons per annum. Ger- 

 many, France, and other countries of the world 

 exhibit similar gains. Even Italy, where the 

 useful arts have been most neglected, has pro- 

 duced about 300,000 tons of iron-ore, of which 

 a small amount is there worked into finished 

 iron. The artistic sense of her people is seen 

 in the architectural work her blacksmiths make 

 in hammered iron. 



The introduction into open-hearth steel- 

 making of the Pernot furnace with its revolv- 

 ing saucer-shaped hearth, and of the Ponsard 

 furnace with its modernization of the ancient 

 process, are the latest steps in the improvement 

 of steel-making apparatus; and the dephos- 

 phorizing process of Thomas and Gilchrist, by 

 permitting the use of hitherto condemned ores, 

 will prove a grand step in the reduction of cost 

 of Bessemer steel, which must hasten greatly 

 that inevitable change which will, ere long, 

 replace malleable iron by steel in all of its uses. 

 Good mild steel can at last be made cheaper 

 than good iron. This is the grandest of all the 

 industrial revolutions that have affected the 

 iron-trades ; and it will be of hardly inferior 

 importance to the world than was the intro- 

 duction of puddled iron a century ago. 



Steel is employed in every department of 

 iron-work ; and that most remarkable of all its 

 many grades, Whitworth's compressed metal, is 

 now at last coming into commercial importance, 

 of which are being made shafts for the largest 

 steamships, and ordnance that has no equal in 

 strength and endurance. Any size desired can 

 now be made in cast-steel, and 100-ton ingots, 

 shaped under 80-ton hammers, are turned out 

 in one European establishment. 



The progress of mechanical art is well illus- 

 trated by the changes which have taken place 

 in textile manufactures. According to Atkin- 

 son, a century ago one person in each family 

 was compelled to work, day in and day out, 

 nearly the whole year, to furnish homespun 

 and dress goods for the rest ; to-day, such has 

 been the progress in the introduction of mech- 

 anism and automata, that one day's work in 

 the year will, on the average, be sufficient to 

 enable each wol-ker to supply himself with all 

 needed cotton and woolen fabrics. Speeds of 

 cotton spindles have risen, during the last two 



