784 



SCIENCE. 



[N. S. Vol. XI. No. 281. 



is the record in graphical form were made 

 in 1893 by Messrs. Marks and Barraclough 

 in the course of regular graduate work in 



the mechanical laboratories of Sibley Col- 

 lege.* The writer had always anticipated 

 useful employment of such alloys, since the 

 properties of magnesium became familiar 

 to him, in the experimental use of the 

 metal for signal purposes in army and 

 navy, ' in the sixties, ' with the assistance 

 of Admiral Luce and of General Myer, 

 then Chief Signal OtBcer of the Army of 

 the United States. 



The volatility and combustibility of the 

 lighter metal are elements of difficulty in its 

 use in alloys, especially with those, as 

 copper, which have a high temperature of 

 fusion ; but a little care and sometimes 

 very simple special precautions will be 

 found to readily evade such obstructions to 

 its use.j The metal, weighing about two- 



* Mr. Marks is now Assistant Professor of Mecban- 

 ical Engineering at Harvard University ancl Mr. 

 Barracough has charge of the Department of Electrical 

 Engineering at the University of Sidney, N. S. W., 

 of which institution be is an alumnus. Mr. Marks 

 is a graduate of the University of London and of 

 Mason College, Birmingham, England. 



t The writer employed magnesium for illuminating 

 and for signal purposes about the close of the civil 

 war (1864-65), and, while stationed at the U. S. 

 Naval Academy (1865-71) experimented with a va- 

 riety of signal apparatus devised by himself for long- 

 distance work, as above. The most successful forms 

 of apparatus for this application of the metal were 

 constructed for the use of magnesium in powder, in 

 which a suitable proportion of sand was used to in- 

 sure free flow as well as economy. The most success- 



thirds as much as aluminium and between 

 one-fourth and one-fifth as much as iron 

 or steel, has a more than proportional 

 strength, and pieces of the metals having 

 similar size will carry more nearly equal 

 loads. The first at all complete studies of 

 the constructive value of this metal and its 

 alloys were made, on the initiative of the 

 writer, as above, in the laboratories of Sib- 

 ley College ; to which laboratories he had 

 turned over his collected material for that 

 purpose, mainly, at the time, with a view 

 to securing some definite knowledge of its 

 value for the purposes of ' aeronautic en- 

 gineering, ' and with the intention, actually 

 carried into effect, of reporting the outcome 

 to the International Engineering Congress 

 at Chicago in 1893. The result was to show 

 that aluminium might be considerably 

 strengthened by alloying with magnesium in 

 small quantities as above ; but that the al- 

 loying metal was itself stronger than the al- 

 loys, and that the presence of aluminium 

 reduced the strength of magnesium. 



The best comparison of these metals and 

 their alloj's is that by comparing the lengths 

 of bars of the metal, suspended from one 

 end, that can be carried without breaking. 

 The extreme range of the tenacities of 

 magnesium was between 20,000 and 30,000 

 pounds per square inch, corresponding to a 



ful form for other illumination, as photography, sta- 

 tionary signal lamps, theater tableau work, etc., was 

 the ribbon lamp, of which latter a large number were 

 in use when the electric light entered the field and 

 threw them out. See ' A New Marine Signal Light,' 

 describing this apparatus (patented iu May, 1866), 

 Journal Franklin Institute, 1867, E. H. Thurston, in 

 which paper the writer gives the costs of signalling : 

 sixty cents by the magnesium apparatus employed by 

 him, and six dollars for the same message sent by the 

 then usual Coston signals. The marine apparatus 

 was taken by Admiral Luce on his cruise to the Med- 

 iterranean in the summer of 1S66, and the army sig- 

 nal was employed by General Myer about Washing- 

 ton. The latter is now in the possession of the 

 writer. It was built from the designs of the writer by 

 the American Magnesium Co. of Boston. 



